<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2026 Workiva-->
<!--r:019e4774-a05d-7d91-ae60-bce1f205dee1,g:47d56b70-4fcd-4792-9ae3-5e85196551c7-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.nmrk.com/role/Cover" xlink:type="simple" xlink:href="nmrk-20260630.xsd#Cover"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/Cover" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentInformationTable_019e4774-a4e0-75c9-9651-3a6d592288ae" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentInformationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentInformationTable_019e4774-a4e0-75c9-9651-3a6d592288ae" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7bad-bb12-a16b43235fb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_DocumentInformationTable_019e4774-a4e0-75c9-9651-3a6d592288ae" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7bad-bb12-a16b43235fb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-7bad-bb12-a16b43235fb6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7bad-bb12-a16b43235fb6" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-7bad-bb12-a16b43235fb6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-728c-b2d2-dc7d57d5acb5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7bad-bb12-a16b43235fb6" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-728c-b2d2-dc7d57d5acb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a4e0-7c7e-bd92-fb229760bf30" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-728c-b2d2-dc7d57d5acb5" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a4e0-7c7e-bd92-fb229760bf30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a4e0-7a19-bf1e-be1c84f80559" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-728c-b2d2-dc7d57d5acb5" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a4e0-7a19-bf1e-be1c84f80559" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentType_019e4774-a4e0-7eb8-8e09-067da25753ea" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentType"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentType_019e4774-a4e0-7eb8-8e09-067da25753ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentQuarterlyReport_019e4774-a4e0-7dba-a88e-6ff19bad0aad" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentQuarterlyReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentQuarterlyReport_019e4774-a4e0-7dba-a88e-6ff19bad0aad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentPeriodEndDate_019e4774-a4e0-7291-ba53-acac4b7871fe" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentPeriodEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentPeriodEndDate_019e4774-a4e0-7291-ba53-acac4b7871fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CurrentFiscalYearEndDate_019e4774-a4e0-70ed-a05a-849bdd8901d3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CurrentFiscalYearEndDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_CurrentFiscalYearEndDate_019e4774-a4e0-70ed-a05a-849bdd8901d3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentTransitionReport_019e4774-a4e0-718b-9b5b-6ede56b3f0de" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentTransitionReport"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentTransitionReport_019e4774-a4e0-718b-9b5b-6ede56b3f0de" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFileNumber_019e4774-a4e0-7065-9370-290c4a1c7be9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFileNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityFileNumber_019e4774-a4e0-7065-9370-290c4a1c7be9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityRegistrantName_019e4774-a4e0-7e86-8cf9-e39952b5886b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityRegistrantName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityRegistrantName_019e4774-a4e0-7e86-8cf9-e39952b5886b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityIncorporationStateCountryCode_019e4774-a4e0-70e9-98c2-4fbbb91ea4fa" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityIncorporationStateCountryCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityIncorporationStateCountryCode_019e4774-a4e0-70e9-98c2-4fbbb91ea4fa" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityTaxIdentificationNumber_019e4774-a4e0-77c3-9a5c-53c9cee9a478" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityTaxIdentificationNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityTaxIdentificationNumber_019e4774-a4e0-77c3-9a5c-53c9cee9a478" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressAddressLine1_019e4774-a4e0-71cb-877f-bf73fe408914" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressAddressLine1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityAddressAddressLine1_019e4774-a4e0-71cb-877f-bf73fe408914" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressCityOrTown_019e4774-a4e0-7bfb-ae86-27ed94ec0fb7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressCityOrTown"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityAddressCityOrTown_019e4774-a4e0-7bfb-ae86-27ed94ec0fb7" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressStateOrProvince_019e4774-a4e0-7c8f-acd9-4297dc6af9f4" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressStateOrProvince"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityAddressStateOrProvince_019e4774-a4e0-7c8f-acd9-4297dc6af9f4" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityAddressPostalZipCode_019e4774-a4e0-73f5-81c6-179822babef7" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityAddressPostalZipCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityAddressPostalZipCode_019e4774-a4e0-73f5-81c6-179822babef7" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_CityAreaCode_019e4774-a4e0-7b07-96d9-f2a46a2c96c1" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_CityAreaCode"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_CityAreaCode_019e4774-a4e0-7b07-96d9-f2a46a2c96c1" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LocalPhoneNumber_019e4774-a4e0-7e1b-9707-55a5d2b95d16" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LocalPhoneNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_LocalPhoneNumber_019e4774-a4e0-7e1b-9707-55a5d2b95d16" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_Security12bTitle_019e4774-a4e0-7fe5-8234-9c5b887e4072" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_Security12bTitle"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_Security12bTitle_019e4774-a4e0-7fe5-8234-9c5b887e4072" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_TradingSymbol_019e4774-a4e0-729f-9e46-2bd918fdcbd0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_TradingSymbol"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_TradingSymbol_019e4774-a4e0-729f-9e46-2bd918fdcbd0" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_SecurityExchangeName_019e4774-a4e0-74d9-9729-3485f38a4cb2" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_SecurityExchangeName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_SecurityExchangeName_019e4774-a4e0-74d9-9729-3485f38a4cb2" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCurrentReportingStatus_019e4774-a4e0-7306-8735-09017f3bd54a" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCurrentReportingStatus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityCurrentReportingStatus_019e4774-a4e0-7306-8735-09017f3bd54a" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityInteractiveDataCurrent_019e4774-a4e0-7444-8e43-e800779ad669" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityInteractiveDataCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityInteractiveDataCurrent_019e4774-a4e0-7444-8e43-e800779ad669" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityFilerCategory_019e4774-a4e0-7629-bd2a-ab52bfbb2f9d" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityFilerCategory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityFilerCategory_019e4774-a4e0-7629-bd2a-ab52bfbb2f9d" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntitySmallBusiness_019e4774-a4e0-7d74-b75c-e0eddcbd69c0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntitySmallBusiness"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntitySmallBusiness_019e4774-a4e0-7d74-b75c-e0eddcbd69c0" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityEmergingGrowthCompany_019e4774-a4e0-7bdd-8886-2baec8650eb3" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityEmergingGrowthCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityEmergingGrowthCompany_019e4774-a4e0-7bdd-8886-2baec8650eb3" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityShellCompany_019e4774-a4e0-7149-b04d-c574d611d36b" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityShellCompany"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityShellCompany_019e4774-a4e0-7149-b04d-c574d611d36b" xlink:type="arc" order="23"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCommonStockSharesOutstanding_019e4774-a4e0-74f2-b0a6-c9d8525797d0" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityCommonStockSharesOutstanding_019e4774-a4e0-74f2-b0a6-c9d8525797d0" xlink:type="arc" order="24"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AmendmentFlag_019e4774-a4e0-7c3e-8161-0f171e027769" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_AmendmentFlag"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_AmendmentFlag_019e4774-a4e0-7c3e-8161-0f171e027769" xlink:type="arc" order="25"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalYearFocus_019e4774-a4e0-7ac8-ad48-dce817e3b4a5" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalYearFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentFiscalYearFocus_019e4774-a4e0-7ac8-ad48-dce817e3b4a5" xlink:type="arc" order="26"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_DocumentFiscalPeriodFocus_019e4774-a4e0-7e01-9a7c-a99e50500dac" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_DocumentFiscalPeriodFocus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_DocumentFiscalPeriodFocus_019e4774-a4e0-7e01-9a7c-a99e50500dac" xlink:type="arc" order="27"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityCentralIndexKey_019e4774-a4e0-7805-9613-3ee43704e248" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityCentralIndexKey"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_DocumentInformationLineItems_019e4774-a4e0-7205-828f-768bb55f12f2" xlink:to="loc_dei_EntityCentralIndexKey_019e4774-a4e0-7805-9613-3ee43704e248" xlink:type="arc" order="28"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETS"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4774-a4e0-73f9-9c35-a74630dc5e8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4774-a4e0-7a0f-ba0e-aabdb2ae704e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a4e0-73f9-9c35-a74630dc5e8c" xlink:to="loc_us-gaap_StatementTable_019e4774-a4e0-7a0f-ba0e-aabdb2ae704e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7689-b6a0-104349038e1f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a4e0-7a0f-ba0e-aabdb2ae704e" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7689-b6a0-104349038e1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-7689-b6a0-104349038e1f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7689-b6a0-104349038e1f" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-7689-b6a0-104349038e1f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-721d-a476-fb7a31739c54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a4e0-7689-b6a0-104349038e1f" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-721d-a476-fb7a31739c54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a4e0-72f6-8142-7b6506685e98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-721d-a476-fb7a31739c54" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a4e0-72f6-8142-7b6506685e98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a4e0-7f6f-875c-cf0e00d4aa64" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a4e0-721d-a476-fb7a31739c54" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a4e0-7f6f-875c-cf0e00d4aa64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a4e0-7463-b656-7d45b4cc5827" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a4e0-7a0f-ba0e-aabdb2ae704e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a4e0-7463-b656-7d45b4cc5827" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a4e0-7463-b656-7d45b4cc5827_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a4e0-7463-b656-7d45b4cc5827" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a4e0-7463-b656-7d45b4cc5827_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a4e0-7277-b2c0-8d4ae982bf54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a4e0-7463-b656-7d45b4cc5827" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a4e0-7277-b2c0-8d4ae982bf54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrelatedPartyMember_019e4774-a4e0-7c84-b8d7-5af3135c1832" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonrelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a4e0-7277-b2c0-8d4ae982bf54" xlink:to="loc_us-gaap_NonrelatedPartyMember_019e4774-a4e0-7c84-b8d7-5af3135c1832" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a4e0-73f9-9c35-a74630dc5e8c" xlink:to="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e4774-a4e0-7979-bd89-75ebe107aaf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_019e4774-a4e0-7979-bd89-75ebe107aaf3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedCashAndInvestmentsCurrent_019e4774-a4e0-7848-b5e9-18d35841eea8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndInvestmentsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:to="loc_us-gaap_RestrictedCashAndInvestmentsCurrent_019e4774-a4e0-7848-b5e9-18d35841eea8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019e4774-a4e0-742f-b651-943ba2869526" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019e4774-a4e0-742f-b651-943ba2869526" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019e4774-a4e0-7464-870d-516959887886" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019e4774-a4e0-7464-870d-516959887886" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsCurrent_019e4774-a4e0-7ca1-a469-ac217565cf98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:to="loc_us-gaap_OtherAssetsCurrent_019e4774-a4e0-7ca1-a469-ac217565cf98" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_019e4774-a4e0-71c7-bdd9-c03a8668bdf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_019e4774-a4e0-7def-b830-a403a3ee3f46" xlink:to="loc_us-gaap_AssetsCurrent_019e4774-a4e0-71c7-bdd9-c03a8668bdf9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e4774-a4e0-7e41-b852-cb05824f081a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_Goodwill_019e4774-a4e0-7e41-b852-cb05824f081a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_019e4774-a4e0-7c02-9a69-29101521c166" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_ServicingAsset_019e4774-a4e0-7c02-9a69-29101521c166" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent_019e4774-a4e0-7ba0-ae72-8d7295b9d03b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent_019e4774-a4e0-7ba0-ae72-8d7295b9d03b" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e4774-a4e0-719f-94b0-b2a32bf97de0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e4774-a4e0-719f-94b0-b2a32bf97de0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019e4774-a4e0-78ac-ba7c-7ae4737889d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019e4774-a4e0-78ac-ba7c-7ae4737889d2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e4774-a4e0-7ed5-9827-e96ae02fc62b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e4774-a4e0-7ed5-9827-e96ae02fc62b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_019e4774-a4e0-7025-a42f-3dd884d9281c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_019e4774-a4e0-7025-a42f-3dd884d9281c" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e4774-a4e0-7acf-b9d1-d4ebe448365a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_019e4774-a4e0-705f-98f4-38eab729e66f" xlink:to="loc_us-gaap_Assets_019e4774-a4e0-7acf-b9d1-d4ebe448365a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a4e0-73f9-9c35-a74630dc5e8c" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarehouseAgreementBorrowings_019e4774-a4e0-7ab6-85ec-8e00f1aa65ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarehouseAgreementBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:to="loc_us-gaap_WarehouseAgreementBorrowings_019e4774-a4e0-7ab6-85ec-8e00f1aa65ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019e4774-a4e0-71c6-b87f-768205e1f719" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:to="loc_us-gaap_EmployeeRelatedLiabilitiesCurrent_019e4774-a4e0-71c6-b87f-768205e1f719" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent_019e4774-a4e0-73d5-9d10-524714a55209" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:to="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent_019e4774-a4e0-73d5-9d10-524714a55209" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableOtherCurrent_019e4774-a4e0-7b2e-89f7-2bd040b9874d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableOtherCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:to="loc_us-gaap_AccountsPayableOtherCurrent_019e4774-a4e0-7b2e-89f7-2bd040b9874d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_019e4774-a4e0-7852-a12c-a4c551394996" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_019e4774-a4e0-7a95-a67a-49b1cc439612" xlink:to="loc_us-gaap_LiabilitiesCurrent_019e4774-a4e0-7852-a12c-a4c551394996" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019e4774-a4e0-732c-bbc0-0a3c1491a9da" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019e4774-a4e0-732c-bbc0-0a3c1491a9da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e4774-a4e0-7ae2-94ff-298805eb9b45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e4774-a4e0-7ae2-94ff-298805eb9b45" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_019e4774-a4e0-7c44-ae73-bfb6231795a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_019e4774-a4e0-7c44-ae73-bfb6231795a6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Liabilities_019e4774-a4e0-7117-8b4d-efeec15ed469" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Liabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_Liabilities_019e4774-a4e0-7117-8b4d-efeec15ed469" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_019e4774-a4e0-71e0-97d8-57a8bd91ed49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_CommitmentsAndContingencies_019e4774-a4e0-71e0-97d8-57a8bd91ed49" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_019e4774-a4e0-7d20-944c-44b7c5fde485" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_TemporaryEquityCarryingAmountIncludingPortionAttributableToNoncontrollingInterests_019e4774-a4e0-7d20-944c-44b7c5fde485" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_019e4774-a4e0-767a-af3c-b62aa2334ac8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_CommonStockValue_019e4774-a4e0-767a-af3c-b62aa2334ac8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_019e4774-a4e0-7ee4-bb98-657561d451c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_019e4774-a4e0-7ee4-bb98-657561d451c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e4774-a4e0-78b4-bfae-a8208c1c97b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_019e4774-a4e0-78b4-bfae-a8208c1c97b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonValue_019e4774-a4e0-7e98-9718-7dd37ffd1184" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_TreasuryStockCommonValue_019e4774-a4e0-7e98-9718-7dd37ffd1184" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e4774-a4e0-71ec-874b-10862372a4c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_019e4774-a4e0-71ec-874b-10862372a4c3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_019e4774-a4e0-7e11-a88c-aeed1779596d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_StockholdersEquity_019e4774-a4e0-7e11-a88c-aeed1779596d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MinorityInterest_019e4774-a4e0-7626-ad0b-913c115c2f44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MinorityInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_MinorityInterest_019e4774-a4e0-7626-ad0b-913c115c2f44" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4774-a4e0-7030-973a-9c48acad0470" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_019e4774-a4e0-7575-bdf4-ddfb7eb2b322" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4774-a4e0-7030-973a-9c48acad0470" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e4774-a4e0-7d78-9dbd-f2d3f51ef9d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_019e4774-a4e0-7066-8b74-968f268c8112" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_019e4774-a4e0-7d78-9dbd-f2d3f51ef9d0" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDBALANCESHEETSParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4774-a5a8-77ed-858a-2bb6dc3d2cc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:to="loc_us-gaap_StatementTable_019e4774-a5a8-77ed-858a-2bb6dc3d2cc8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7101-a9c7-1f742937a6bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-77ed-858a-2bb6dc3d2cc8" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7101-a9c7-1f742937a6bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7101-a9c7-1f742937a6bc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7101-a9c7-1f742937a6bc" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7101-a9c7-1f742937a6bc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7ddd-a718-26b9a8b42af7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7101-a9c7-1f742937a6bc" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7ddd-a718-26b9a8b42af7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a8-7b64-b230-c5f26f36033f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7ddd-a718-26b9a8b42af7" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a8-7b64-b230-c5f26f36033f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a5a8-75fd-9826-abf5b38e793d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7ddd-a718-26b9a8b42af7" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a5a8-75fd-9826-abf5b38e793d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e4774-a5a8-7dde-8e0a-5b515e9cd6cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e4774-a5a8-7dde-8e0a-5b515e9cd6cb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019e4774-a5a8-73a4-b864-8a9b1cb4ceef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019e4774-a5a8-73a4-b864-8a9b1cb4ceef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_019e4774-a5a8-7ae7-9dd7-c912d7591f8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:to="loc_us-gaap_CommonStockSharesIssued_019e4774-a5a8-7ae7-9dd7-c912d7591f8c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a8-7418-bc49-2150a6d4bd09" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a8-7418-bc49-2150a6d4bd09" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_019e4774-a5a8-73e2-8e37-dbfedbe7b73d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7d00-b371-71a36026c015" xlink:to="loc_us-gaap_TreasuryStockCommonShares_019e4774-a5a8-73e2-8e37-dbfedbe7b73d" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFOPERATIONS" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4774-a5a8-7cc4-b4e0-024c5a2cb139" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_StatementTable_019e4774-a5a8-7cc4-b4e0-024c5a2cb139" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e4774-a5a8-7a13-b5f1-a51a81114396" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-7cc4-b4e0-024c5a2cb139" xlink:to="loc_srt_ProductOrServiceAxis_019e4774-a5a8-7a13-b5f1-a51a81114396" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7a13-b5f1-a51a81114396_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a8-7a13-b5f1-a51a81114396" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7a13-b5f1-a51a81114396_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7367-9c0b-30fe6cc46cee" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a8-7a13-b5f1-a51a81114396" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7367-9c0b-30fe6cc46cee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ManagementServicesServicingFeesAndOtherMember_019e4774-a5a8-744c-ba8d-6b8e1ef2f1ee" xlink:href="nmrk-20260630.xsd#nmrk_ManagementServicesServicingFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7367-9c0b-30fe6cc46cee" xlink:to="loc_nmrk_ManagementServicesServicingFeesAndOtherMember_019e4774-a5a8-744c-ba8d-6b8e1ef2f1ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LeasingAndOtherCommissionsMember_019e4774-a5a8-7554-ba1f-1d668a442a6b" xlink:href="nmrk-20260630.xsd#nmrk_LeasingAndOtherCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7367-9c0b-30fe6cc46cee" xlink:to="loc_nmrk_LeasingAndOtherCommissionsMember_019e4774-a5a8-7554-ba1f-1d668a442a6b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CapitalMarketsMember_019e4774-a5a8-748a-a9a2-450f58493bb8" xlink:href="nmrk-20260630.xsd#nmrk_CapitalMarketsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7367-9c0b-30fe6cc46cee" xlink:to="loc_nmrk_CapitalMarketsMember_019e4774-a5a8-748a-a9a2-450f58493bb8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_019e4774-a5a8-76b3-b682-b60a764401c3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_RevenuesAbstract_019e4774-a5a8-76b3-b682-b60a764401c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4774-a5a8-7a82-bf65-e4ff6962053e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_019e4774-a5a8-76b3-b682-b60a764401c3" xlink:to="loc_us-gaap_Revenues_019e4774-a5a8-7a82-bf65-e4ff6962053e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostDirectLabor_019e4774-a5a8-7f10-b769-cc4f1ee9ad4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostDirectLabor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_us-gaap_CostDirectLabor_019e4774-a5a8-7f10-b769-cc4f1ee9ad4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_EquityBasedCompensationAndAllocationsOfNetIncomeToLimitedPartnershipUnitsAndFPUs_019e4774-a5a8-7e57-88be-f554a9a36868" xlink:href="nmrk-20260630.xsd#nmrk_EquityBasedCompensationAndAllocationsOfNetIncomeToLimitedPartnershipUnitsAndFPUs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_nmrk_EquityBasedCompensationAndAllocationsOfNetIncomeToLimitedPartnershipUnitsAndFPUs_019e4774-a5a8-7e57-88be-f554a9a36868" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019e4774-a5a8-74e4-8476-aa3577be99e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019e4774-a5a8-74e4-8476-aa3577be99e2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpense_019e4774-a5a8-78b7-8e4c-f31b3e7a008f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpense_019e4774-a5a8-78b7-8e4c-f31b3e7a008f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019e4774-a5a8-712c-af28-87647910a4b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_us-gaap_ProfessionalFees_019e4774-a5a8-712c-af28-87647910a4b0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019e4774-a5a8-7572-99c5-a1fd0042ae73" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_us-gaap_DepreciationAndAmortization_019e4774-a5a8-7572-99c5-a1fd0042ae73" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostsAndExpenses_019e4774-a5a8-7d1d-b38a-7853ccd58bdf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostsAndExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CostsAndExpensesAbstract_019e4774-a5a8-7f1d-bc6d-dcaac5db90b3" xlink:to="loc_us-gaap_CostsAndExpenses_019e4774-a5a8-7d1d-b38a-7853ccd58bdf" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019e4774-a5a8-798b-af95-f3618c1df1d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019e4774-a5a8-798b-af95-f3618c1df1d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_019e4774-a5a8-7b20-a3ed-e49db4e4fc50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_OperatingIncomeLoss_019e4774-a5a8-7b20-a3ed-e49db4e4fc50" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019e4774-a5a8-70a5-a929-f70167eaa5bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019e4774-a5a8-70a5-a929-f70167eaa5bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e4774-a5a8-7fd2-ad5c-1acfa1b89159" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_019e4774-a5a8-7fd2-ad5c-1acfa1b89159" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_019e4774-a5a8-7863-b034-402e537be649" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_019e4774-a5a8-7863-b034-402e537be649" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e4774-a5a8-7888-9fe2-63481001a5b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_ProfitLoss_019e4774-a5a8-7888-9fe2-63481001a5b6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019e4774-a5a8-74c2-9ff3-daeeda1dc9a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_019e4774-a5a8-74c2-9ff3-daeeda1dc9a9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_019e4774-a5a8-7ff4-9b29-5c103d9de6c9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_NetIncomeLoss_019e4774-a5a8-7ff4-9b29-5c103d9de6c9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_019e4774-a5a8-7c72-96a3-1a38e841ff4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7ced-b9fc-993346cb7f70" xlink:to="loc_us-gaap_EarningsPerShareAbstract_019e4774-a5a8-7c72-96a3-1a38e841ff4c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasicAbstract_019e4774-a5a8-7fd7-9c88-6d31f890b595" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasicAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019e4774-a5a8-7c72-96a3-1a38e841ff4c" xlink:to="loc_us-gaap_EarningsPerShareBasicAbstract_019e4774-a5a8-7fd7-9c88-6d31f890b595" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019e4774-a5a8-72cd-9bb5-5f639ade401e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019e4774-a5a8-7fd7-9c88-6d31f890b595" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic_019e4774-a5a8-72cd-9bb5-5f639ade401e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_019e4774-a5a8-7723-95d8-2a77bd84da16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019e4774-a5a8-7fd7-9c88-6d31f890b595" xlink:to="loc_us-gaap_EarningsPerShareBasic_019e4774-a5a8-7723-95d8-2a77bd84da16" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019e4774-a5a8-74e7-86c4-a5b61ad0f91a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareBasicAbstract_019e4774-a5a8-7fd7-9c88-6d31f890b595" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_019e4774-a5a8-74e7-86c4-a5b61ad0f91a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDilutedAbstract_019e4774-a5a8-7921-af66-870b2f351039" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDilutedAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_019e4774-a5a8-7c72-96a3-1a38e841ff4c" xlink:to="loc_us-gaap_EarningsPerShareDilutedAbstract_019e4774-a5a8-7921-af66-870b2f351039" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_019e4774-a5a8-7fd8-8706-2ce08da9a7b3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019e4774-a5a8-7921-af66-870b2f351039" xlink:to="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted_019e4774-a5a8-7fd8-8706-2ce08da9a7b3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_019e4774-a5a8-7e1c-9438-d39ba3089720" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019e4774-a5a8-7921-af66-870b2f351039" xlink:to="loc_us-gaap_EarningsPerShareDiluted_019e4774-a5a8-7e1c-9438-d39ba3089720" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019e4774-a5a8-755a-9e0e-b470619dc11d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareDilutedAbstract_019e4774-a5a8-7921-af66-870b2f351039" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_019e4774-a5a8-755a-9e0e-b470619dc11d" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITY" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4774-a5a8-7e8c-9333-b857bc4c49dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4774-a5a8-7638-b521-b29e334b8096" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7e8c-9333-b857bc4c49dc" xlink:to="loc_us-gaap_StatementTable_019e4774-a5a8-7638-b521-b29e334b8096" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7a55-8715-429cd92c10fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-7638-b521-b29e334b8096" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7a55-8715-429cd92c10fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7a55-8715-429cd92c10fd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7a55-8715-429cd92c10fd" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7a55-8715-429cd92c10fd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7615-8fa3-f31313573185" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7a55-8715-429cd92c10fd" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7615-8fa3-f31313573185" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a8-733d-9ae5-f170a190e87c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7615-8fa3-f31313573185" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a8-733d-9ae5-f170a190e87c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a5a8-7617-817f-584a91bac586" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7615-8fa3-f31313573185" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a5a8-7617-817f-584a91bac586" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-777a-ba00-74b5126a3852" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-7638-b521-b29e334b8096" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-777a-ba00-74b5126a3852" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-777a-ba00-74b5126a3852_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-777a-ba00-74b5126a3852" xlink:to="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-777a-ba00-74b5126a3852_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-777a-ba00-74b5126a3852" xlink:to="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e4774-a5a8-7706-8908-94d12ece6f71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:to="loc_us-gaap_CommonStockMember_019e4774-a5a8-7706-8908-94d12ece6f71" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_019e4774-a5a8-7d68-8712-8e8b71c692b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_019e4774-a5a8-7d68-8712-8e8b71c692b8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_019e4774-a5a8-754a-943e-7358120e77d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:to="loc_us-gaap_TreasuryStockCommonMember_019e4774-a5a8-754a-943e-7358120e77d0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_019e4774-a5a8-7126-b5bb-78985f7d9e44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:to="loc_us-gaap_RetainedEarningsMember_019e4774-a5a8-7126-b5bb-78985f7d9e44" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_019e4774-a5a8-70fd-9cc7-4a3c7514d5bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:to="loc_us-gaap_AociIncludingPortionAttributableToNoncontrollingInterestMember_019e4774-a5a8-70fd-9cc7-4a3c7514d5bb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncontrollingInterestMember_019e4774-a5a8-79e8-b01f-799c0c0e0e83" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncontrollingInterestMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7a05-8aea-0fe52fe66ad3" xlink:to="loc_us-gaap_NoncontrollingInterestMember_019e4774-a5a8-79e8-b01f-799c0c0e0e83" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019fd33e-76ad-7918-a6ed-5b2023686e75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-7638-b521-b29e334b8096" xlink:to="loc_us-gaap_AwardTypeAxis_019fd33e-76ad-7918-a6ed-5b2023686e75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fd33e-76ad-7918-a6ed-5b2023686e75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019fd33e-76ad-7918-a6ed-5b2023686e75" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fd33e-76ad-7918-a6ed-5b2023686e75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fd33e-76ad-7e79-b4fb-2722a42e1e1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019fd33e-76ad-7918-a6ed-5b2023686e75" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fd33e-76ad-7e79-b4fb-2722a42e1e1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FoundingWorkingPartnerUnitsMember_019fd33e-76ad-760b-b65f-8135b13098b0" xlink:href="nmrk-20260630.xsd#nmrk_FoundingWorkingPartnerUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019fd33e-76ad-7e79-b4fb-2722a42e1e1a" xlink:to="loc_nmrk_FoundingWorkingPartnerUnitsMember_019fd33e-76ad-760b-b65f-8135b13098b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7e8c-9333-b857bc4c49dc" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4774-a5a8-78d2-ba14-fcf2b03e6120" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4774-a5a8-78d2-ba14-fcf2b03e6120" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_019e4774-a5a8-7da4-98ba-fb63cbc8b03b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_ProfitLoss_019e4774-a5a8-7da4-98ba-fb63cbc8b03b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019e4774-a5a8-7d7d-b1c4-1660c623a02d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_019e4774-a5a8-7d7d-b1c4-1660c623a02d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019f93c8-e154-73b8-929c-e26759e08085" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_019f93c8-e154-73b8-929c-e26759e08085" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_019e4774-a5a8-7c2b-9ad2-91da44a0a762" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_DividendsCommonStockCash_019e4774-a5a8-7c2b-9ad2-91da44a0a762" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_StockIssuedDuringPeriodValueConversionOfUnitsFairValueAdjustments_019e4774-a5a8-7a0e-b878-7cc8bd23c65e" xlink:href="nmrk-20260630.xsd#nmrk_StockIssuedDuringPeriodValueConversionOfUnitsFairValueAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_nmrk_StockIssuedDuringPeriodValueConversionOfUnitsFairValueAdjustments_019e4774-a5a8-7a0e-b878-7cc8bd23c65e" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NoncontrollingInterestEarningsDistributionsToLimitedPartnershipInterestsAndOtherNoncontrollingInterest_019e4774-a5a8-71d0-ae99-51d4e0662f8c" xlink:href="nmrk-20260630.xsd#nmrk_NoncontrollingInterestEarningsDistributionsToLimitedPartnershipInterestsAndOtherNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_nmrk_NoncontrollingInterestEarningsDistributionsToLimitedPartnershipInterestsAndOtherNoncontrollingInterest_019e4774-a5a8-71d0-ae99-51d4e0662f8c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NoncontrollingInterestIncreaseDecreaseFromGrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterests_019e4774-a5a8-7415-8795-879be25f17c7" xlink:href="nmrk-20260630.xsd#nmrk_NoncontrollingInterestIncreaseDecreaseFromGrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterests"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_nmrk_NoncontrollingInterestIncreaseDecreaseFromGrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterests_019e4774-a5a8-7415-8795-879be25f17c7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_EquityBasedCompensationContributionsOfCapitalToAndFromCantor_019e4774-a5a8-7263-bbdb-f5b58ba4e672" xlink:href="nmrk-20260630.xsd#nmrk_EquityBasedCompensationContributionsOfCapitalToAndFromCantor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_nmrk_EquityBasedCompensationContributionsOfCapitalToAndFromCantor_019e4774-a5a8-7263-bbdb-f5b58ba4e672" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredParValueMethod_019e4774-a5a8-76e0-9476-e26a412e2495" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredParValueMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredParValueMethod_019e4774-a5a8-76e0-9476-e26a412e2495" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited_019e4774-a5a8-7dde-9313-852f9f16dac5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited_019e4774-a5a8-7dde-9313-852f9f16dac5" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e4774-a5a8-77c6-b6f3-82fb44aa476e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_019e4774-a5a8-77c6-b6f3-82fb44aa476e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityOther_019e4774-a5a8-7acd-a3e6-68f6d5382a68" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a8-7e4a-98c9-fda14186bfea" xlink:to="loc_us-gaap_StockholdersEquityOther_019e4774-a5a8-7acd-a3e6-68f6d5382a68" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_019e4774-a5a8-7eb0-b420-c6139f8dcaa2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019fd33e-76ad-73d3-ac36-8d7822271ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7e8c-9333-b857bc4c49dc" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019fd33e-76ad-73d3-ac36-8d7822271ac4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITYParenthetical" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITYParenthetical"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CONDENSEDCONSOLIDATEDSTATEMENTSOFCHANGESINEQUITYParenthetical" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_019e4774-a5a8-79d8-adde-b19122486794" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_StatementTable_019e4774-a5a8-79d8-adde-b19122486794" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7b55-9c0c-eaad14d95c6f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-79d8-adde-b19122486794" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7b55-9c0c-eaad14d95c6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7b55-9c0c-eaad14d95c6f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7b55-9c0c-eaad14d95c6f" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7b55-9c0c-eaad14d95c6f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7adb-bbb9-ffd461f173ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-7b55-9c0c-eaad14d95c6f" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7adb-bbb9-ffd461f173ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a8-74ab-8c96-687f791859bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-7adb-bbb9-ffd461f173ca" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a8-74ab-8c96-687f791859bf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-7030-b1b5-31405b24e0db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-79d8-adde-b19122486794" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-7030-b1b5-31405b24e0db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7030-b1b5-31405b24e0db_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-7030-b1b5-31405b24e0db" xlink:to="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7030-b1b5-31405b24e0db_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7c5d-8b6b-d988da23e0f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_019e4774-a5a8-7030-b1b5-31405b24e0db" xlink:to="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7c5d-8b6b-d988da23e0f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e4774-a5a8-78a3-94bf-1cb6c0a7e8c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_019e4774-a5a8-7c5d-8b6b-d988da23e0f5" xlink:to="loc_us-gaap_CommonStockMember_019e4774-a5a8-78a3-94bf-1cb6c0a7e8c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019f93c8-0b5e-7913-8f23-2462b2c65f75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_019e4774-a5a8-79d8-adde-b19122486794" xlink:to="loc_us-gaap_AwardTypeAxis_019f93c8-0b5e-7913-8f23-2462b2c65f75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93c8-0b5e-7913-8f23-2462b2c65f75_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019f93c8-0b5e-7913-8f23-2462b2c65f75" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93c8-0b5e-7913-8f23-2462b2c65f75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93c8-0b5e-7408-9f78-7e4c171a9c49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019f93c8-0b5e-7913-8f23-2462b2c65f75" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93c8-0b5e-7408-9f78-7e4c171a9c49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FoundingWorkingPartnerUnitsMember_019f93c8-0b5e-7be8-b64c-68a3c3e40b0b" xlink:href="nmrk-20260630.xsd#nmrk_FoundingWorkingPartnerUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93c8-0b5e-7408-9f78-7e4c171a9c49" xlink:to="loc_nmrk_FoundingWorkingPartnerUnitsMember_019f93c8-0b5e-7be8-b64c-68a3c3e40b0b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019f93c8-0b5e-7103-b546-a9e2d118966b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019f93c8-0b5e-7103-b546-a9e2d118966b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019e4774-a5a8-71a2-b98f-9e5eb37befb5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_019e4774-a5a8-71a2-b98f-9e5eb37befb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_GrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterestsAndIssuanceOfCommonStockShares_019e4774-a5a8-7f59-bfa1-9ec51d122026" xlink:href="nmrk-20260630.xsd#nmrk_GrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterestsAndIssuanceOfCommonStockShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_nmrk_GrantOfExchangeabilityRedemptionAndIssuanceOfLimitedPartnershipInterestsAndIssuanceOfCommonStockShares_019e4774-a5a8-7f59-bfa1-9ec51d122026" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a8-7000-bf0e-690b9ecc8b36" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a8-7000-bf0e-690b9ecc8b36" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited_019e4774-a5a8-76cd-93bc-878223ba51e9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited_019e4774-a5a8-76cd-93bc-878223ba51e9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019e4774-a5a8-7088-94b0-1374fd0bd2d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019e4774-a5a8-7088-94b0-1374fd0bd2d3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019e4774-a5a8-7105-860b-38ae513ba7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareCashPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_019e4774-a5a8-7b50-85bb-cf7b23a2d3ed" xlink:to="loc_us-gaap_CommonStockDividendsPerShareCashPaid_019e4774-a5a8-7105-860b-38ae513ba7b8" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/LimitedPartnershipInterestsinNewmarkHoldingsandBGCHoldingsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#LimitedPartnershipInterestsinNewmarkHoldingsandBGCHoldingsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/LimitedPartnershipInterestsinNewmarkHoldingsandBGCHoldingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a5a8-79e2-ac65-fe210f5f88e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a5a8-79e2-ac65-fe210f5f88e7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a5a8-714a-811a-401bde01b231" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a5a8-79e2-ac65-fe210f5f88e7" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a5a8-714a-811a-401bde01b231" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a5a8-714a-811a-401bde01b231_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a5a8-714a-811a-401bde01b231" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a5a8-714a-811a-401bde01b231_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a5a8-7d43-beb3-43f0b9c1f853" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a5a8-714a-811a-401bde01b231" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a5a8-7d43-beb3-43f0b9c1f853" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a5a8-78e5-a782-e74c0a7fc37a" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a5a8-7d43-beb3-43f0b9c1f853" xlink:to="loc_srt_ParentCompanyMember_019e4774-a5a8-78e5-a782-e74c0a7fc37a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-70e2-9e65-a63eadc86cc7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a5a8-79e2-ac65-fe210f5f88e7" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-70e2-9e65-a63eadc86cc7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-70e2-9e65-a63eadc86cc7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-70e2-9e65-a63eadc86cc7" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-70e2-9e65-a63eadc86cc7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-76f0-a6e4-6f304147f051" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a8-70e2-9e65-a63eadc86cc7" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-76f0-a6e4-6f304147f051" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a8-72f3-b657-4781db652da2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-76f0-a6e4-6f304147f051" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a8-72f3-b657-4781db652da2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a5a8-7038-9524-2cc45944794b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a8-76f0-a6e4-6f304147f051" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a5a8-7038-9524-2cc45944794b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsExchangeRatio_019e4774-a5a8-7edf-bc8b-7f2e6d04c554" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsExchangeRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:to="loc_nmrk_LimitedPartnershipUnitsExchangeRatio_019e4774-a5a8-7edf-bc8b-7f2e6d04c554" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PostTerminationAwardPayoutPeriod_019e4774-a5a8-7acb-8e98-f36cb2a8b4fd" xlink:href="nmrk-20260630.xsd#nmrk_PostTerminationAwardPayoutPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:to="loc_nmrk_PostTerminationAwardPayoutPeriod_019e4774-a5a8-7acb-8e98-f36cb2a8b4fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PercentageOfProfitsAllocatedToPreferredPartnershipUnits_019e4774-a5a8-7b2f-839b-d45286fa0a0d" xlink:href="nmrk-20260630.xsd#nmrk_PercentageOfProfitsAllocatedToPreferredPartnershipUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:to="loc_nmrk_PercentageOfProfitsAllocatedToPreferredPartnershipUnits_019e4774-a5a8-7b2f-839b-d45286fa0a0d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PercentageOfProfitsAllocatedToPreferredPartnershipUnitsAnnualPercentageRate_019e4774-a5a8-7a3b-8e18-182494137ac4" xlink:href="nmrk-20260630.xsd#nmrk_PercentageOfProfitsAllocatedToPreferredPartnershipUnitsAnnualPercentageRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:to="loc_nmrk_PercentageOfProfitsAllocatedToPreferredPartnershipUnitsAnnualPercentageRate_019e4774-a5a8-7a3b-8e18-182494137ac4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OtherOwnershipInterestsUnitsExchangeable_019e4774-a5a8-7d01-86cb-c6eb631706ec" xlink:href="nmrk-20260630.xsd#nmrk_OtherOwnershipInterestsUnitsExchangeable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a5a8-7706-90ae-bef118a99589" xlink:to="loc_nmrk_OtherOwnershipInterestsUnitsExchangeable_019e4774-a5a8-7d01-86cb-c6eb631706ec" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#SummaryofSignificantAccountingPoliciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/SummaryofSignificantAccountingPoliciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_019e4774-a5a8-7e2d-8179-f2c541aa0e56" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_019e4774-a5a8-7e2d-8179-f2c541aa0e56" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_019e4774-a5a8-7607-8ae8-2aa2028ec904" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_019e4774-a5a8-7e2d-8179-f2c541aa0e56" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_019e4774-a5a8-7607-8ae8-2aa2028ec904" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4774-a5a8-7607-8ae8-2aa2028ec904_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4774-a5a8-7607-8ae8-2aa2028ec904" xlink:to="loc_us-gaap_SegmentDomain_019e4774-a5a8-7607-8ae8-2aa2028ec904_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_019e4774-a5a8-7cae-b51e-1a50025b8e59" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_019e4774-a5a8-7607-8ae8-2aa2028ec904" xlink:to="loc_us-gaap_SegmentDomain_019e4774-a5a8-7cae-b51e-1a50025b8e59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ReportableSegmentMember_019e4774-a5a8-77dd-b0c1-ac2f3e66d591" xlink:href="nmrk-20260630.xsd#nmrk_ReportableSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_019e4774-a5a8-7cae-b51e-1a50025b8e59" xlink:to="loc_nmrk_ReportableSegmentMember_019e4774-a5a8-77dd-b0c1-ac2f3e66d591" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ProvisionReversalForRiskSharingObligationsAndSettlement_019e4774-a5a8-7e81-8310-5d3e0408801c" xlink:href="nmrk-20260630.xsd#nmrk_ProvisionReversalForRiskSharingObligationsAndSettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_nmrk_ProvisionReversalForRiskSharingObligationsAndSettlement_019e4774-a5a8-7e81-8310-5d3e0408801c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuarantyLiabilities_019e4774-a5a8-71e4-8f93-6df66c32fc54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuarantyLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_GuarantyLiabilities_019e4774-a5a8-71e4-8f93-6df66c32fc54" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease_019e4774-a5a8-7ad2-83e1-f307e06863c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivablePeriodIncreaseDecrease_019e4774-a5a8-7ad2-83e1-f307e06863c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_019e4774-a5a8-743c-9bea-66a16b4b7ab3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_019e4774-a5a8-743c-9bea-66a16b4b7ab3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019e4774-a5a8-7c92-9085-be368312723d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_019e4774-a5a8-7c92-9085-be368312723d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_019e4774-a5a8-7a99-b84c-dd1017133ad4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_019e4774-a5a8-7a99-b84c-dd1017133ad4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NumberOfReportableSegments_019e4774-a5a8-7322-b339-67c05439dde9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NumberOfReportableSegments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_NumberOfReportableSegments_019e4774-a5a8-7322-b339-67c05439dde9" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4774-a5a8-7c7b-8b0d-76dc648ec95a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_Revenues_019e4774-a5a8-7c7b-8b0d-76dc648ec95a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestAndFeeIncomeLoansHeldForSaleMortgages_019e4774-a5a8-7e5e-9eff-11ca9e20c79d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestAndFeeIncomeLoansHeldForSaleMortgages"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_InterestAndFeeIncomeLoansHeldForSaleMortgages_019e4774-a5a8-7e5e-9eff-11ca9e20c79d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019e4774-a5a8-7dc0-a0fe-3604f925253c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019e4774-a5a8-7dc0-a0fe-3604f925253c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_EquityBasedCompensationAndAllocationsOfNetIncomeToLimitedPartnershipUnitsAndFPUs_019e4774-a5a8-7b6c-ab17-65bf60bdb3f9" xlink:href="nmrk-20260630.xsd#nmrk_EquityBasedCompensationAndAllocationsOfNetIncomeToLimitedPartnershipUnitsAndFPUs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_nmrk_EquityBasedCompensationAndAllocationsOfNetIncomeToLimitedPartnershipUnitsAndFPUs_019e4774-a5a8-7b6c-ab17-65bf60bdb3f9" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_019e4774-a5a8-75a2-a544-c68f0a112200" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_OperatingExpenses_019e4774-a5a8-75a2-a544-c68f0a112200" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationAndAmortization_019e4774-a5a8-7d63-9cea-c55df1482ec8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_DepreciationAndAmortization_019e4774-a5a8-7d63-9cea-c55df1482ec8" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019e4774-a5a8-7146-bf5f-4fbc56e98fbd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_ProfessionalFees_019e4774-a5a8-7146-bf5f-4fbc56e98fbd" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019e4774-a5a8-77b9-ba0b-66dd7fcbbe6c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestIncomeExpenseNonoperatingNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_InterestIncomeExpenseNonoperatingNet_019e4774-a5a8-77b9-ba0b-66dd7fcbbe6c" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_019e4774-a5a8-74e4-b17b-5ded9030d67b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_019e4774-a5a8-76c0-b0f7-de94d2ea0b57" xlink:to="loc_us-gaap_Assets_019e4774-a5a8-74e4-b17b-5ded9030d67b" xlink:type="arc" order="15"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/SummaryofSignificantAccountingPoliciesScheduleofRevenuebySegmentDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#SummaryofSignificantAccountingPoliciesScheduleofRevenuebySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/SummaryofSignificantAccountingPoliciesScheduleofRevenuebySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_019e4774-a5a8-7d68-907b-68bdf8e55d3f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019e4774-a5a8-795f-be16-2d639d50de37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_019e4774-a5a8-7d68-907b-68bdf8e55d3f" xlink:to="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019e4774-a5a8-795f-be16-2d639d50de37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e4774-a5a8-75c3-95e9-a41177189085" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEntityWideInformationRevenueFromExternalCustomersByProductsAndServicesTable_019e4774-a5a8-795f-be16-2d639d50de37" xlink:to="loc_srt_ProductOrServiceAxis_019e4774-a5a8-75c3-95e9-a41177189085" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-75c3-95e9-a41177189085_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a8-75c3-95e9-a41177189085" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-75c3-95e9-a41177189085_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7960-93e8-e6a58153c33f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a8-75c3-95e9-a41177189085" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7960-93e8-e6a58153c33f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ManagementServicesServicingFeesAndOtherMember_019e4774-a5a8-77ec-a2ed-e749fbfd62ed" xlink:href="nmrk-20260630.xsd#nmrk_ManagementServicesServicingFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7960-93e8-e6a58153c33f" xlink:to="loc_nmrk_ManagementServicesServicingFeesAndOtherMember_019e4774-a5a8-77ec-a2ed-e749fbfd62ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LeasingAndOtherCommissionsMember_019e4774-a5a8-7202-925a-44adc5c1aa61" xlink:href="nmrk-20260630.xsd#nmrk_LeasingAndOtherCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7960-93e8-e6a58153c33f" xlink:to="loc_nmrk_LeasingAndOtherCommissionsMember_019e4774-a5a8-7202-925a-44adc5c1aa61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CapitalMarketsMember_019e4774-a5a8-74dc-ab9f-f737c9fad59b" xlink:href="nmrk-20260630.xsd#nmrk_CapitalMarketsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a8-7960-93e8-e6a58153c33f" xlink:to="loc_nmrk_CapitalMarketsMember_019e4774-a5a8-74dc-ab9f-f737c9fad59b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4774-a5a8-71ce-be69-a3be6dbe259f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems_019e4774-a5a8-7d68-907b-68bdf8e55d3f" xlink:to="loc_us-gaap_Revenues_019e4774-a5a8-71ce-be69-a3be6dbe259f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/SummaryofSignificantAccountingPoliciesScheduleofRevenuebyGeographicAreaDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#SummaryofSignificantAccountingPoliciesScheduleofRevenuebyGeographicAreaDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/SummaryofSignificantAccountingPoliciesScheduleofRevenuebyGeographicAreaDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a8-7acf-8ed3-2a1a6df9de3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a8-7756-b602-22c4592eb689" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a8-7acf-8ed3-2a1a6df9de3a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a8-7756-b602-22c4592eb689" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019e4774-a5a8-7050-9e61-cd0380179c99" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a8-7756-b602-22c4592eb689" xlink:to="loc_srt_StatementGeographicalAxis_019e4774-a5a8-7050-9e61-cd0380179c99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7050-9e61-cd0380179c99_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019e4774-a5a8-7050-9e61-cd0380179c99" xlink:to="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7050-9e61-cd0380179c99_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7702-b624-f6e3ab5b9086" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019e4774-a5a8-7050-9e61-cd0380179c99" xlink:to="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7702-b624-f6e3ab5b9086" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_019e4774-a5a8-7b5b-8420-e5947caee02f" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7702-b624-f6e3ab5b9086" xlink:to="loc_country_US_019e4774-a5a8-7b5b-8420-e5947caee02f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_GB_019e4774-a5a8-73c6-adf1-5bd97f9e6fc5" xlink:href="https://xbrl.sec.gov/country/2026/country-2026.xsd#country_GB"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7702-b624-f6e3ab5b9086" xlink:to="loc_country_GB_019e4774-a5a8-73c6-adf1-5bd97f9e6fc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OtherGeographicalAreasMember_019e4774-a5a8-7650-993d-eab2c5a0e5dc" xlink:href="nmrk-20260630.xsd#nmrk_OtherGeographicalAreasMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4774-a5a8-7702-b624-f6e3ab5b9086" xlink:to="loc_nmrk_OtherGeographicalAreasMember_019e4774-a5a8-7650-993d-eab2c5a0e5dc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4774-a5a8-7e4d-8e26-778a7bb75e31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a8-7acf-8ed3-2a1a6df9de3a" xlink:to="loc_us-gaap_Revenues_019e4774-a5a8-7e4d-8e26-778a7bb75e31" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/AcquisitionsScheduleofComponentsofPurchaseConsiderationTransferredandPreliminaryAllocationofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#AcquisitionsScheduleofComponentsofPurchaseConsiderationTransferredandPreliminaryAllocationofAssetsAcquiredandLiabilitiesAssumedDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/AcquisitionsScheduleofComponentsofPurchaseConsiderationTransferredandPreliminaryAllocationofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-76a0-b802-b4cffd315fdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e4774-a5a9-78e2-848f-c1a4d7ce1ac9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-76a0-b802-b4cffd315fdc" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e4774-a5a9-78e2-848f-c1a4d7ce1ac9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7a65-8faa-76b141ba8785" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e4774-a5a9-78e2-848f-c1a4d7ce1ac9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7a65-8faa-76b141ba8785" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7a65-8faa-76b141ba8785_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7a65-8faa-76b141ba8785" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7a65-8faa-76b141ba8785_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7835-8e4a-dcbb908f8acc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7a65-8faa-76b141ba8785" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7835-8e4a-dcbb908f8acc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A2025AcquisitionsMember_019e4774-a5a9-7702-911b-9a8d5141a492" xlink:href="nmrk-20260630.xsd#nmrk_A2025AcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7835-8e4a-dcbb908f8acc" xlink:to="loc_nmrk_A2025AcquisitionsMember_019e4774-a5a9-7702-911b-9a8d5141a492" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_019e4774-a5a9-7dfd-8041-881e71a4f14b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferredAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-76a0-b802-b4cffd315fdc" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_019e4774-a5a9-7dfd-8041-881e71a4f14b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_019e4774-a5a9-7260-b2ce-b5d3f8472ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_019e4774-a5a9-7dfd-8041-881e71a4f14b" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_019e4774-a5a9-7260-b2ce-b5d3f8472ac4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019e4774-a5a9-7d14-991e-7b51cda174b8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationConsiderationTransferredAbstract_019e4774-a5a9-7dfd-8041-881e71a4f14b" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019e4774-a5a9-7d14-991e-7b51cda174b8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-76a0-b802-b4cffd315fdc" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019e4774-a5a9-71b6-92a9-5d78db45f59f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_019e4774-a5a9-71b6-92a9-5d78db45f59f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e4774-a5a9-7be3-9cfe-843b3b6ba290" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_Goodwill_019e4774-a5a9-7be3-9cfe-843b3b6ba290" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019e4774-a5a9-7876-8598-8db094fc9f1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibleAssetsOtherThanGoodwill_019e4774-a5a9-7876-8598-8db094fc9f1a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019e4774-a5a9-7622-800c-38e1150fc167" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_019e4774-a5a9-7622-800c-38e1150fc167" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019e4774-a5a9-7b35-85e9-31f18f4c9338" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_019e4774-a5a9-7b35-85e9-31f18f4c9338" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssets_019e4774-a5a9-7c6f-aaac-54e1f890b577" xlink:href="nmrk-20260630.xsd#nmrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_nmrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherAssets_019e4774-a5a9-7c6f-aaac-54e1f890b577" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation_019e4774-a5a9-7580-b398-d3453db59ed4" xlink:href="nmrk-20260630.xsd#nmrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_nmrk_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAccruedCompensation_019e4774-a5a9-7580-b398-d3453db59ed4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_019e4774-a5a9-75af-bcd3-9f85a18e11f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_019e4774-a5a9-75af-bcd3-9f85a18e11f5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019e4774-a5a9-7c59-b66a-a248c0a6583e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssetsAbstract_019e4774-a5a9-7f94-a63f-32f7b0f31592" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_019e4774-a5a9-7c59-b66a-a248c0a6583e" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/AcquisitionsNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#AcquisitionsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/AcquisitionsNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-7356-812f-9d1581730c86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e4774-a5a9-7e31-b022-aece036e8fc5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-7356-812f-9d1581730c86" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e4774-a5a9-7e31-b022-aece036e8fc5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7650-8e38-d9638b0e7473" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_019e4774-a5a9-7e31-b022-aece036e8fc5" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7650-8e38-d9638b0e7473" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7650-8e38-d9638b0e7473_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7650-8e38-d9638b0e7473" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7650-8e38-d9638b0e7473_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7286-b782-358cc748079b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a5a9-7650-8e38-d9638b0e7473" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7286-b782-358cc748079b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A2025AcquisitionsMember_019e4774-a5a9-7910-956b-1de388f97a72" xlink:href="nmrk-20260630.xsd#nmrk_A2025AcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a5a9-7286-b782-358cc748079b" xlink:to="loc_nmrk_A2025AcquisitionsMember_019e4774-a5a9-7910-956b-1de388f97a72" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019e4774-a5a9-72cd-a0a6-0bb58af4d2c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-7356-812f-9d1581730c86" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_019e4774-a5a9-72cd-a0a6-0bb58af4d2c0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_019e4774-a5a9-7d6d-85dc-484ef6039f0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-7356-812f-9d1581730c86" xlink:to="loc_us-gaap_Goodwill_019e4774-a5a9-7d6d-85dc-484ef6039f0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019e4774-a5a9-7b98-b6db-ca269b0d74fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_019e4774-a5a9-7356-812f-9d1581730c86" xlink:to="loc_us-gaap_BusinessCombinationProFormaInformationRevenueOfAcquireeSinceAcquisitionDateActual_019e4774-a5a9-7b98-b6db-ca269b0d74fc" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/StockTransactionsandUnitPurchasesNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#StockTransactionsandUnitPurchasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/StockTransactionsandUnitPurchasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7ed4-a0f2-1e61fb674a58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7ed4-a0f2-1e61fb674a58" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-787d-89dc-b71977229cff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7ed4-a0f2-1e61fb674a58" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-787d-89dc-b71977229cff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-787d-89dc-b71977229cff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-787d-89dc-b71977229cff" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-787d-89dc-b71977229cff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7c32-9524-4a74f5eb88cb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-787d-89dc-b71977229cff" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7c32-9524-4a74f5eb88cb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a9-7b7f-aca4-b5ef2b996da4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7c32-9524-4a74f5eb88cb" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a9-7b7f-aca4-b5ef2b996da4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a5a9-7231-a36b-8c65b0bd9aba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7c32-9524-4a74f5eb88cb" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a5a9-7231-a36b-8c65b0bd9aba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NumberOfAuthorizedClassesOfCommonStock_019e4774-a5a9-7d97-9bb5-b0da2edcdb1f" xlink:href="nmrk-20260630.xsd#nmrk_NumberOfAuthorizedClassesOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_nmrk_NumberOfAuthorizedClassesOfCommonStock_019e4774-a5a9-7d97-9bb5-b0da2edcdb1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NumberOfVotesPerCommonShare_019e4774-a5a9-70ba-91fc-5e882b4eab11" xlink:href="nmrk-20260630.xsd#nmrk_NumberOfVotesPerCommonShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_nmrk_NumberOfVotesPerCommonShare_019e4774-a5a9-70ba-91fc-5e882b4eab11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_019e4774-a5a9-7405-bb4e-eaa01c215190" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_019e4774-a5a9-7405-bb4e-eaa01c215190" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e4774-a5a9-7c7e-93a9-ee911b464071" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_019e4774-a5a9-7c7e-93a9-ee911b464071" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ConversionOfCommonStock_019e4774-a5a9-7303-8b49-2a8cb58c1bb5" xlink:href="nmrk-20260630.xsd#nmrk_ConversionOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_nmrk_ConversionOfCommonStock_019e4774-a5a9-7303-8b49-2a8cb58c1bb5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a9-74b9-9b70-7d62925a6ae7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a9-74b9-9b70-7d62925a6ae7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e4774-a5a9-75b7-b6fe-15c7b5b68868" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e4774-a5a9-75b7-b6fe-15c7b5b68868" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a9-7f26-b0de-f3bc39d5c8b2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a9-7f26-b0de-f3bc39d5c8b2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e4774-a5a9-72c5-b0d5-60baf8fdc049" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7b14-8e57-7cc534e3f51c" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e4774-a5a9-72c5-b0d5-60baf8fdc049" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/StockTransactionsandUnitPurchasesScheduleofChangesinSharesofCommonStockOutstandingDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#StockTransactionsandUnitPurchasesScheduleofChangesinSharesofCommonStockOutstandingDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/StockTransactionsandUnitPurchasesScheduleofChangesinSharesofCommonStockOutstandingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7cf1-8531-44914d0f8159" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7cf5-bd90-256cf637ea0c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7cf1-8531-44914d0f8159" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7cf5-bd90-256cf637ea0c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7a81-8997-099cb2af5e88" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7cf5-bd90-256cf637ea0c" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7a81-8997-099cb2af5e88" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7a81-8997-099cb2af5e88_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7a81-8997-099cb2af5e88" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7a81-8997-099cb2af5e88_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7154-a4b5-600689c03f4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7a81-8997-099cb2af5e88" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7154-a4b5-600689c03f4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a9-7375-aa36-bac019542cea" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7154-a4b5-600689c03f4a" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a9-7375-aa36-bac019542cea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a5a9-7494-98bc-0b50bc7e761f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7cf5-bd90-256cf637ea0c" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a5a9-7494-98bc-0b50bc7e761f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a5a9-7494-98bc-0b50bc7e761f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a5a9-7494-98bc-0b50bc7e761f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a5a9-7494-98bc-0b50bc7e761f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a5a9-711c-8c41-3da4193f918e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a5a9-7494-98bc-0b50bc7e761f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a5a9-711c-8c41-3da4193f918e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a5a9-7038-89a9-20059faee5fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a5a9-711c-8c41-3da4193f918e" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a5a9-7038-89a9-20059faee5fc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a9-7e9e-a1e8-394ec773e0f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7cf1-8531-44914d0f8159" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a9-7e9e-a1e8-394ec773e0f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a9-7a07-98bd-6155fedf3912" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a9-7e9e-a1e8-394ec773e0f3" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a9-7a07-98bd-6155fedf3912" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareIssuanceAbstract_019e4774-a5a9-7f4b-96f3-eee0a81dd922" xlink:href="nmrk-20260630.xsd#nmrk_ShareIssuanceAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_019e4774-a5a9-7e9e-a1e8-394ec773e0f3" xlink:to="loc_nmrk_ShareIssuanceAbstract_019e4774-a5a9-7f4b-96f3-eee0a81dd922" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ExchangeOrRedemptionForLimitedPartnershipUnit_019e4774-a5a9-7565-a88b-58d76da124c6" xlink:href="nmrk-20260630.xsd#nmrk_ExchangeOrRedemptionForLimitedPartnershipUnit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ShareIssuanceAbstract_019e4774-a5a9-7f4b-96f3-eee0a81dd922" xlink:to="loc_nmrk_ExchangeOrRedemptionForLimitedPartnershipUnit_019e4774-a5a9-7565-a88b-58d76da124c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019e4774-a5a9-7c62-ae1d-3e0401a2ba4e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ShareIssuanceAbstract_019e4774-a5a9-7f4b-96f3-eee0a81dd922" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019e4774-a5a9-7c62-ae1d-3e0401a2ba4e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019e4774-a5a9-72bc-9bbd-134c3f26cdf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ShareIssuanceAbstract_019e4774-a5a9-7f4b-96f3-eee0a81dd922" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_019e4774-a5a9-72bc-9bbd-134c3f26cdf1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a9-7eae-8760-f47885a0d34e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ShareIssuanceAbstract_019e4774-a5a9-7f4b-96f3-eee0a81dd922" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a9-7eae-8760-f47885a0d34e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_019e4774-a5a9-7ecb-97ce-42a8cf79d5a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/StockTransactionsandUnitPurchasesScheduleofShareRepurchaseActivityDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#StockTransactionsandUnitPurchasesScheduleofShareRepurchaseActivityDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/StockTransactionsandUnitPurchasesScheduleofShareRepurchaseActivityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7612-bcae-50f782ab434d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7671-baf4-2ade80a4ae15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfStockByClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7612-bcae-50f782ab434d" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7671-baf4-2ade80a4ae15" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7d51-9142-adf418824969" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_019e4774-a5a9-7671-baf4-2ade80a4ae15" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7d51-9142-adf418824969" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7d51-9142-adf418824969_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7d51-9142-adf418824969" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7d51-9142-adf418824969_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7817-b218-9a0707f3f93e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a5a9-7d51-9142-adf418824969" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7817-b218-9a0707f3f93e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a5a9-7ee8-81ac-364676118ade" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a5a9-7817-b218-9a0707f3f93e" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a5a9-7ee8-81ac-364676118ade" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a9-7644-b266-6e6d7ff2288c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7612-bcae-50f782ab434d" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019e4774-a5a9-7644-b266-6e6d7ff2288c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e4774-a5a9-72e1-9e6b-d76551a40e29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7612-bcae-50f782ab434d" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_019e4774-a5a9-72e1-9e6b-d76551a40e29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e4774-a5a9-702a-af95-d78f340b2f3d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_019e4774-a5a9-7612-bcae-50f782ab434d" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_019e4774-a5a9-702a-af95-d78f340b2f3d" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CapitalandLiquidityRequirementsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CapitalandLiquidityRequirementsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CapitalandLiquidityRequirementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019e4774-a5a9-7de0-be48-b6178e6abd99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019e4774-a5a9-7784-978b-907f43d666d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019e4774-a5a9-7de0-be48-b6178e6abd99" xlink:to="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019e4774-a5a9-7784-978b-907f43d666d0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfArrangementAxis_019e4774-a5a9-77f3-bc7d-8d5dece5d48e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsTable_019e4774-a5a9-7784-978b-907f43d666d0" xlink:to="loc_us-gaap_TypeOfArrangementAxis_019e4774-a5a9-77f3-bc7d-8d5dece5d48e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e4774-a5a9-77f3-bc7d-8d5dece5d48e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_019e4774-a5a9-77f3-bc7d-8d5dece5d48e" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e4774-a5a9-77f3-bc7d-8d5dece5d48e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e4774-a5a9-728c-b4fc-91c5ef8870f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_019e4774-a5a9-77f3-bc7d-8d5dece5d48e" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e4774-a5a9-728c-b4fc-91c5ef8870f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_SellerServicerAgreementsMember_019e4774-a5a9-7901-a678-a81a08499d3a" xlink:href="nmrk-20260630.xsd#nmrk_SellerServicerAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_019e4774-a5a9-728c-b4fc-91c5ef8870f4" xlink:to="loc_nmrk_SellerServicerAgreementsMember_019e4774-a5a9-7901-a678-a81a08499d3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ExcessCapital_019e4774-a5a9-7fa8-b5b8-49bfc27de987" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExcessCapital"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019e4774-a5a9-7de0-be48-b6178e6abd99" xlink:to="loc_us-gaap_ExcessCapital_019e4774-a5a9-7fa8-b5b8-49bfc27de987" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PercentageOfLiquidityRequirementOfOutstandingPrincipalOfTargetedAffordableHousingLoansServiced_019e4774-a5a9-7f61-97b5-e9b2bde01416" xlink:href="nmrk-20260630.xsd#nmrk_PercentageOfLiquidityRequirementOfOutstandingPrincipalOfTargetedAffordableHousingLoansServiced"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019e4774-a5a9-7de0-be48-b6178e6abd99" xlink:to="loc_nmrk_PercentageOfLiquidityRequirementOfOutstandingPrincipalOfTargetedAffordableHousingLoansServiced_019e4774-a5a9-7f61-97b5-e9b2bde01416" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OutstandingBorrowerAdvancesToInvestorsReimbursementPeriod_019e4774-a5a9-7b2e-911a-cf98be33f793" xlink:href="nmrk-20260630.xsd#nmrk_OutstandingBorrowerAdvancesToInvestorsReimbursementPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019e4774-a5a9-7de0-be48-b6178e6abd99" xlink:to="loc_nmrk_OutstandingBorrowerAdvancesToInvestorsReimbursementPeriod_019e4774-a5a9-7b2e-911a-cf98be33f793" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OutstandingBorrowerAdvancesToInvestors_019e4774-a5a9-7169-a6a0-a681951dbc8a" xlink:href="nmrk-20260630.xsd#nmrk_OutstandingBorrowerAdvancesToInvestors"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ComplianceWithRegulatoryCapitalRequirementsUnderBankingRegulationsLineItems_019e4774-a5a9-7de0-be48-b6178e6abd99" xlink:to="loc_nmrk_OutstandingBorrowerAdvancesToInvestors_019e4774-a5a9-7169-a6a0-a681951dbc8a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/LoansHeldforSaleatFairValueScheduleofLoansHeldforSaleatCostBasisandFairValueDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#LoansHeldforSaleatFairValueScheduleofLoansHeldforSaleatCostBasisandFairValueDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/LoansHeldforSaleatFairValueScheduleofLoansHeldforSaleatCostBasisandFairValueDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019e4774-a5a9-79ed-8bcc-e267d62b4cf8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsNotesAndLoansReceivableLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019e4774-a5a9-7861-85ac-f6e06d9e7aca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019e4774-a5a9-79ed-8bcc-e267d62b4cf8" xlink:to="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019e4774-a5a9-7861-85ac-f6e06d9e7aca" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_019e4774-a5a9-7d86-8e03-92d418ca6608" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAccountsNotesLoansAndFinancingReceivableTable_019e4774-a5a9-7861-85ac-f6e06d9e7aca" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_019e4774-a5a9-7d86-8e03-92d418ca6608" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e4774-a5a9-7d86-8e03-92d418ca6608_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019e4774-a5a9-7d86-8e03-92d418ca6608" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e4774-a5a9-7d86-8e03-92d418ca6608_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019e4774-a5a9-711a-ba26-f670143c572d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_019e4774-a5a9-7d86-8e03-92d418ca6608" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019e4774-a5a9-711a-ba26-f670143c572d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e4774-a5a9-7c27-a6d4-ad385d03e38f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_019e4774-a5a9-711a-ba26-f670143c572d" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e4774-a5a9-7c27-a6d4-ad385d03e38f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019e4774-a5a9-750a-8368-12611110c743" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e4774-a5a9-7c27-a6d4-ad385d03e38f" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_019e4774-a5a9-750a-8368-12611110c743" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019e4774-a5a9-76a7-8b9b-e79d0c27f95e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_019e4774-a5a9-7c27-a6d4-ad385d03e38f" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_019e4774-a5a9-76a7-8b9b-e79d0c27f95e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019e4774-a5a9-7bc2-a519-419c5f0a60b4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccountsNotesAndLoansReceivableLineItems_019e4774-a5a9-79ed-8bcc-e267d62b4cf8" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019e4774-a5a9-7bc2-a519-419c5f0a60b4" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DerivativesScheduleofFairValueofDerivativeContractsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DerivativesScheduleofFairValueofDerivativeContractsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DerivativesScheduleofFairValueofDerivativeContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e4774-a5a9-7c3f-8582-f97c29674cdc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e4774-a5a9-745d-8f3b-aa5eca0dcf71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e4774-a5a9-7c3f-8582-f97c29674cdc" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e4774-a5a9-745d-8f3b-aa5eca0dcf71" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7061-929e-ebba41e76790" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_019e4774-a5a9-745d-8f3b-aa5eca0dcf71" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7061-929e-ebba41e76790" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7061-929e-ebba41e76790_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7061-929e-ebba41e76790" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7061-929e-ebba41e76790_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-757a-8471-d34e9b15b2cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7061-929e-ebba41e76790" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-757a-8471-d34e9b15b2cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7c17-a18d-50410748fbf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-757a-8471-d34e9b15b2cf" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7c17-a18d-50410748fbf5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_019e4774-a5a9-73ad-b2c8-029170ce6ef4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForwardContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-757a-8471-d34e9b15b2cf" xlink:to="loc_us-gaap_ForwardContractsMember_019e4774-a5a9-73ad-b2c8-029170ce6ef4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_019e4774-a5a9-7cd5-bb40-cc3aa60f8951" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e4774-a5a9-7c3f-8582-f97c29674cdc" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_019e4774-a5a9-7cd5-bb40-cc3aa60f8951" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_019e4774-a5a9-7778-a519-9792b80e4be7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e4774-a5a9-7c3f-8582-f97c29674cdc" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_019e4774-a5a9-7778-a519-9792b80e4be7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_019e4774-a5a9-7b40-a27e-dbdedafbb3bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_019e4774-a5a9-7c3f-8582-f97c29674cdc" xlink:to="loc_us-gaap_DerivativeNotionalAmount_019e4774-a5a9-7b40-a27e-dbdedafbb3bd" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DerivativesNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DerivativesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DerivativesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7f40-a06f-7d26c7771849" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-73da-b95c-e2f0b59bd076" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7f40-a06f-7d26c7771849" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-73da-b95c-e2f0b59bd076" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7956-8645-0b9463d19bfc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-73da-b95c-e2f0b59bd076" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7956-8645-0b9463d19bfc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7956-8645-0b9463d19bfc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7956-8645-0b9463d19bfc" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7956-8645-0b9463d19bfc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7eb7-af3d-97aff82e61c0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7956-8645-0b9463d19bfc" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7eb7-af3d-97aff82e61c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7948-a975-c297798adc4c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7eb7-af3d-97aff82e61c0" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7948-a975-c297798adc4c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-7a9a-a968-8760d2a4b934" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-73da-b95c-e2f0b59bd076" xlink:to="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-7a9a-a968-8760d2a4b934" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7a9a-a968-8760d2a4b934_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-7a9a-a968-8760d2a4b934" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7a9a-a968-8760d2a4b934_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-70c3-b7db-016837e7bae0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-7a9a-a968-8760d2a4b934" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-70c3-b7db-016837e7bae0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019e4774-a5a9-773b-9d49-5fb6190636e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-70c3-b7db-016837e7bae0" xlink:to="loc_us-gaap_NondesignatedMember_019e4774-a5a9-773b-9d49-5fb6190636e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-7a73-a8cb-1c00183b57f7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7f40-a06f-7d26c7771849" xlink:to="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-7a73-a8cb-1c00183b57f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-770b-bfec-312d0a4ac67e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7f40-a06f-7d26c7771849" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-770b-bfec-312d0a4ac67e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DerivativesScheduleofGainsLossesonDerivativeContractsIncludedinCondensedConsolidatedStatementsofOperationsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DerivativesScheduleofGainsLossesonDerivativeContractsIncludedinCondensedConsolidatedStatementsofOperationsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DerivativesScheduleofGainsLossesonDerivativeContractsIncludedinCondensedConsolidatedStatementsofOperationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7adb-a573-319fe173ae8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7adb-a573-319fe173ae8f" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:to="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-75f3-bdaa-fd604471ee7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-75f3-bdaa-fd604471ee7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7af0-a6f3-7531e5259815" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7af0-a6f3-7531e5259815" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019e4774-a5a9-78db-a9eb-6c6714a320df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7af0-a6f3-7531e5259815" xlink:to="loc_us-gaap_NondesignatedMember_019e4774-a5a9-78db-a9eb-6c6714a320df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7112-8be9-bc15251ec983_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7112-8be9-bc15251ec983_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7e8d-b3bc-09bc35f0d776" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7e8d-b3bc-09bc35f0d776" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_019e4774-a5a9-7f09-9bea-e8a0d3c51d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForwardContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:to="loc_us-gaap_ForwardContractsMember_019e4774-a5a9-7f09-9bea-e8a0d3c51d4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019e4774-a5a9-79ea-a66b-b89c9af29b41" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:to="loc_us-gaap_StatementOfIncomeLocationBalanceAxis_019e4774-a5a9-79ea-a66b-b89c9af29b41" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-74e4-b9d2-521ed89d9489" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7adb-a573-319fe173ae8f" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-74e4-b9d2-521ed89d9489" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-7d7f-b76d-d6456c897ea9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-74e4-b9d2-521ed89d9489" xlink:to="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-7d7f-b76d-d6456c897ea9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DerivativesScheduleofGainsLossesonDerivativeContractsIncludedinCondensedConsolidatedStatementsofOperationsDetails_1" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DerivativesScheduleofGainsLossesonDerivativeContractsIncludedinCondensedConsolidatedStatementsofOperationsDetails_1"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DerivativesScheduleofGainsLossesonDerivativeContractsIncludedinCondensedConsolidatedStatementsofOperationsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7adb-a573-319fe173ae8f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7adb-a573-319fe173ae8f" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:to="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-75f3-bdaa-fd604471ee7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-75f3-bdaa-fd604471ee7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7af0-a6f3-7531e5259815" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_019e4774-a5a9-75f3-bdaa-fd604471ee7f" xlink:to="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7af0-a6f3-7531e5259815" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NondesignatedMember_019e4774-a5a9-78db-a9eb-6c6714a320df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NondesignatedMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_019e4774-a5a9-7af0-a6f3-7531e5259815" xlink:to="loc_us-gaap_NondesignatedMember_019e4774-a5a9-78db-a9eb-6c6714a320df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_019e4774-a5a9-7a6a-b2ee-73fd010a046e" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7112-8be9-bc15251ec983_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7112-8be9-bc15251ec983_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_019e4774-a5a9-7112-8be9-bc15251ec983" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7e8d-b3bc-09bc35f0d776" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a5a9-7e8d-b3bc-09bc35f0d776" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_019e4774-a5a9-7f09-9bea-e8a0d3c51d4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForwardContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_019e4774-a5a9-7d88-8036-41e7d30d8209" xlink:to="loc_us-gaap_ForwardContractsMember_019e4774-a5a9-7f09-9bea-e8a0d3c51d4d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-74e4-b9d2-521ed89d9489" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossOnDerivativeNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_019e4774-a5a9-7adb-a573-319fe173ae8f" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-74e4-b9d2-521ed89d9489" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-7d7f-b76d-d6456c897ea9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeGainLossOnDerivativeNet_019e4774-a5a9-74e4-b9d2-521ed89d9489" xlink:to="loc_us-gaap_DerivativeGainLossStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-7d7f-b76d-d6456c897ea9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RevenuesfromContractswithCustomersScheduleofRevenuesfromContractswithCustomersandOurOtherSourcesofRevenuesDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RevenuesfromContractswithCustomersScheduleofRevenuesfromContractswithCustomersandOurOtherSourcesofRevenuesDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RevenuesfromContractswithCustomersScheduleofRevenuesfromContractswithCustomersandOurOtherSourcesofRevenuesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-7bfb-8d86-d376f0fe2a1b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a9-75a3-89dd-97f38eaabcba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-7bfb-8d86-d376f0fe2a1b" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a9-75a3-89dd-97f38eaabcba" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e4774-a5a9-701a-86ed-85520f71dab5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a9-75a3-89dd-97f38eaabcba" xlink:to="loc_srt_ProductOrServiceAxis_019e4774-a5a9-701a-86ed-85520f71dab5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-701a-86ed-85520f71dab5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a9-701a-86ed-85520f71dab5" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-701a-86ed-85520f71dab5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a9-701a-86ed-85520f71dab5" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LeasingAndOtherCommissionsMember_019e4774-a5a9-7f9f-bdc6-b1374271b9d2" xlink:href="nmrk-20260630.xsd#nmrk_LeasingAndOtherCommissionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_nmrk_LeasingAndOtherCommissionsMember_019e4774-a5a9-7f9f-bdc6-b1374271b9d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentAdviceMember_019e4774-a5a9-7d05-8177-811f50afaf8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InvestmentAdviceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_us-gaap_InvestmentAdviceMember_019e4774-a5a9-7d05-8177-811f50afaf8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MortgageBrokerageAndDebtPlacementMember_019e4774-a5a9-757d-8805-419eeee31173" xlink:href="nmrk-20260630.xsd#nmrk_MortgageBrokerageAndDebtPlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_nmrk_MortgageBrokerageAndDebtPlacementMember_019e4774-a5a9-757d-8805-419eeee31173" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ManagementServicesMember_019e4774-a5a9-7d88-868a-25988e535e97" xlink:href="nmrk-20260630.xsd#nmrk_ManagementServicesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_nmrk_ManagementServicesMember_019e4774-a5a9-7d88-868a-25988e535e97" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ServicingMember_019e4774-a5a9-7728-b6ad-bd7cef9803a6" xlink:href="nmrk-20260630.xsd#nmrk_ServicingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_nmrk_ServicingMember_019e4774-a5a9-7728-b6ad-bd7cef9803a6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LoanOriginationsRelatedFeesAndSalesPremiumsNetMember_019e4774-a5a9-7c8d-8d01-2734616b0028" xlink:href="nmrk-20260630.xsd#nmrk_LoanOriginationsRelatedFeesAndSalesPremiumsNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_nmrk_LoanOriginationsRelatedFeesAndSalesPremiumsNetMember_019e4774-a5a9-7c8d-8d01-2734616b0028" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ServicingFeesAndOtherMember_019e4774-a5a9-7e73-a283-aa00df750c96" xlink:href="nmrk-20260630.xsd#nmrk_ServicingFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7304-aea2-dd55e9a9e44c" xlink:to="loc_nmrk_ServicingFeesAndOtherMember_019e4774-a5a9-7e73-a283-aa00df750c96" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e4774-a5a9-79dd-9128-b48eb55e7737" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-7bfb-8d86-d376f0fe2a1b" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e4774-a5a9-79dd-9128-b48eb55e7737" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueNotFromContractWithCustomer_019e4774-a5a9-7875-ad44-18969073034b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueNotFromContractWithCustomer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-7bfb-8d86-d376f0fe2a1b" xlink:to="loc_us-gaap_RevenueNotFromContractWithCustomer_019e4774-a5a9-7875-ad44-18969073034b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4774-a5a9-7550-a3e6-5811f19accbd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-7bfb-8d86-d376f0fe2a1b" xlink:to="loc_us-gaap_Revenues_019e4774-a5a9-7550-a3e6-5811f19accbd" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RevenuesfromContractswithCustomersScheduleofRevenueRemainingPerformanceObligationDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RevenuesfromContractswithCustomersScheduleofRevenueRemainingPerformanceObligationDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RevenuesfromContractswithCustomersScheduleofRevenueRemainingPerformanceObligationDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e4774-a5a9-7303-9e38-f45362f671e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e4774-a5a9-7303-9e38-f45362f671e0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019e4774-a5a9-7382-b7de-f279d14ee44c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e4774-a5a9-7303-9e38-f45362f671e0" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_019e4774-a5a9-7382-b7de-f279d14ee44c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019e4774-a5a9-7365-9401-bf8649802665" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019e4774-a5a9-7365-9401-bf8649802665" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e4774-a5a9-7708-8aa3-2ddd18320933" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e4774-a5a9-7708-8aa3-2ddd18320933" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RevenuesfromContractswithCustomersScheduleofRevenueRemainingPerformanceObligationDetails_1" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RevenuesfromContractswithCustomersScheduleofRevenueRemainingPerformanceObligationDetails_1"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RevenuesfromContractswithCustomersScheduleofRevenueRemainingPerformanceObligationDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e4774-a5a9-7303-9e38-f45362f671e0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_019e4774-a5a9-7303-9e38-f45362f671e0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_019e4774-a5a9-7365-9401-bf8649802665" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_019e4774-a5a9-7365-9401-bf8649802665" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e4774-a5a9-7708-8aa3-2ddd18320933" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_019e4774-a5a9-733a-a55b-3be216e0a424" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_019e4774-a5a9-7708-8aa3-2ddd18320933" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CapitalMarketsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CapitalMarketsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CapitalMarketsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-79e8-9453-e4b51de8a080" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a9-732f-a6fe-e99d5be487cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-79e8-9453-e4b51de8a080" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a9-732f-a6fe-e99d5be487cc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e4774-a5a9-73d5-83c9-1a8d076a3a99" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_019e4774-a5a9-732f-a6fe-e99d5be487cc" xlink:to="loc_srt_ProductOrServiceAxis_019e4774-a5a9-73d5-83c9-1a8d076a3a99" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-73d5-83c9-1a8d076a3a99_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a9-73d5-83c9-1a8d076a3a99" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-73d5-83c9-1a8d076a3a99_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-77d4-a01e-a998f2285845" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a9-73d5-83c9-1a8d076a3a99" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-77d4-a01e-a998f2285845" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CapitalMarketsMember_019e4774-a5a9-7c26-8d48-d16d87d7335b" xlink:href="nmrk-20260630.xsd#nmrk_CapitalMarketsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-77d4-a01e-a998f2285845" xlink:to="loc_nmrk_CapitalMarketsMember_019e4774-a5a9-7c26-8d48-d16d87d7335b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_InvestmentSalesMember_019e4774-a5a9-7c7c-9c84-b75eedafa80c" xlink:href="nmrk-20260630.xsd#nmrk_InvestmentSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_CapitalMarketsMember_019e4774-a5a9-7c26-8d48-d16d87d7335b" xlink:to="loc_nmrk_InvestmentSalesMember_019e4774-a5a9-7c7c-9c84-b75eedafa80c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ServicingMember_019e4774-a5a9-71b9-9183-611837dd5e59" xlink:href="nmrk-20260630.xsd#nmrk_ServicingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_CapitalMarketsMember_019e4774-a5a9-7c26-8d48-d16d87d7335b" xlink:to="loc_nmrk_ServicingMember_019e4774-a5a9-71b9-9183-611837dd5e59" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LoanOriginationsRelatedFeesAndSalesPremiumsNetMember_019e4774-a5a9-7d78-b9e2-1258b3b829b2" xlink:href="nmrk-20260630.xsd#nmrk_LoanOriginationsRelatedFeesAndSalesPremiumsNetMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_CapitalMarketsMember_019e4774-a5a9-7c26-8d48-d16d87d7335b" xlink:to="loc_nmrk_LoanOriginationsRelatedFeesAndSalesPremiumsNetMember_019e4774-a5a9-7d78-b9e2-1258b3b829b2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MortgageBrokerageAndDebtPlacementMember_019e4774-a5a9-774b-a4cc-18d3ebc2f1b0" xlink:href="nmrk-20260630.xsd#nmrk_MortgageBrokerageAndDebtPlacementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_CapitalMarketsMember_019e4774-a5a9-7c26-8d48-d16d87d7335b" xlink:to="loc_nmrk_MortgageBrokerageAndDebtPlacementMember_019e4774-a5a9-774b-a4cc-18d3ebc2f1b0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueNotFromContractWithCustomer_019e4774-a5a9-707f-aab9-77354b47c53e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueNotFromContractWithCustomer"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-79e8-9453-e4b51de8a080" xlink:to="loc_us-gaap_RevenueNotFromContractWithCustomer_019e4774-a5a9-707f-aab9-77354b47c53e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e4774-a5a9-7887-a387-704b470354d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-79e8-9453-e4b51de8a080" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_019e4774-a5a9-7887-a387-704b470354d3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_019e4774-a5a9-7b19-a611-6e681c2ad445" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_019e4774-a5a9-79e8-9453-e4b51de8a080" xlink:to="loc_us-gaap_Revenues_019e4774-a5a9-7b19-a611-6e681c2ad445" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/MortgageServicingRightsNetScheduleofChangesintheCarryingAmountofMortgageServicingRightsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#MortgageServicingRightsNetScheduleofChangesintheCarryingAmountofMortgageServicingRightsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/MortgageServicingRightsNetScheduleofChangesintheCarryingAmountofMortgageServicingRightsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtAmortizedValueLineItems_019e4774-a5a9-79d5-96a0-e26d86466844" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetsAtAmortizedValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAtAmortizedValueTable_019e4774-a5a9-758b-82b7-3f6ddaabf5c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetsAtAmortizedValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ServicingAssetsAtAmortizedValueLineItems_019e4774-a5a9-79d5-96a0-e26d86466844" xlink:to="loc_us-gaap_ServicingAssetsAtAmortizedValueTable_019e4774-a5a9-758b-82b7-3f6ddaabf5c5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7049-bd42-96405c9fbc7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ServicingAssetsAtAmortizedValueTable_019e4774-a5a9-758b-82b7-3f6ddaabf5c5" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7049-bd42-96405c9fbc7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7049-bd42-96405c9fbc7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7049-bd42-96405c9fbc7e" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7049-bd42-96405c9fbc7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-774c-b377-e94f7272c6b0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7049-bd42-96405c9fbc7e" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-774c-b377-e94f7272c6b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MortgageServicingRightsMember_019e4774-a5a9-7c0e-a05c-de1cbcaf1f6a" xlink:href="nmrk-20260630.xsd#nmrk_MortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-774c-b377-e94f7272c6b0" xlink:to="loc_nmrk_MortgageServicingRightsMember_019e4774-a5a9-7c0e-a05c-de1cbcaf1f6a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValueBalanceRollForward_019e4774-a5a9-75e3-a203-616feac4a447" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtAmortizedValueBalanceRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtAmortizedValueLineItems_019e4774-a5a9-79d5-96a0-e26d86466844" xlink:to="loc_us-gaap_ServicingAssetAtAmortizedValueBalanceRollForward_019e4774-a5a9-75e3-a203-616feac4a447" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValue_019e4774-a5a9-7be2-bac7-450b173d92ca" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtAmortizedValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtAmortizedValueBalanceRollForward_019e4774-a5a9-75e3-a203-616feac4a447" xlink:to="loc_us-gaap_ServicingAssetAtAmortizedValue_019e4774-a5a9-7be2-bac7-450b173d92ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValueAdditions_019e4774-a5a9-79f0-8ddd-815247d68e16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtAmortizedValueAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtAmortizedValueBalanceRollForward_019e4774-a5a9-75e3-a203-616feac4a447" xlink:to="loc_us-gaap_ServicingAssetAtAmortizedValueAdditions_019e4774-a5a9-79f0-8ddd-815247d68e16" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValueAmortization1_019e4774-a5a9-779b-9a31-4c11f7ebc638" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtAmortizedValueAmortization1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetAtAmortizedValueBalanceRollForward_019e4774-a5a9-75e3-a203-616feac4a447" xlink:to="loc_us-gaap_ServicingAssetAtAmortizedValueAmortization1_019e4774-a5a9-779b-9a31-4c11f7ebc638" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtAmortizedValue_019e4774-a5a9-7b90-9aae-cb8e785af397" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtAmortizedValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsRollForward_019e4774-a5a9-7c10-b286-74ffef71ae5e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtAmortizedValueLineItems_019e4774-a5a9-79d5-96a0-e26d86466844" xlink:to="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsRollForward_019e4774-a5a9-7c10-b286-74ffef71ae5e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance_019e4774-a5a9-73f4-a31a-67b2889ffa4a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsRollForward_019e4774-a5a9-7c10-b286-74ffef71ae5e" xlink:to="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance_019e4774-a5a9-73f4-a31a-67b2889ffa4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsPeriodIncreaseDecrease_019e4774-a5a9-73eb-aa22-a8831211d251" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsRollForward_019e4774-a5a9-7c10-b286-74ffef71ae5e" xlink:to="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsPeriodIncreaseDecrease_019e4774-a5a9-73eb-aa22-a8831211d251" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance_019e4774-a5a9-74f4-aab3-b1931ee057e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationAllowanceForImpairmentOfRecognizedServicingAssetsBalance"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_019e4774-a5a9-7579-922d-e53791f5755f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ServicingAssetsAtAmortizedValueLineItems_019e4774-a5a9-79d5-96a0-e26d86466844" xlink:to="loc_us-gaap_ServicingAsset_019e4774-a5a9-7579-922d-e53791f5755f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/MortgageServicingRightsNetNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#MortgageServicingRightsNetNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/MortgageServicingRightsNetNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:href="nmrk-20260630.xsd#nmrk_MortgageServicingRightsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MortgageServicingRightsTable_019e4774-a5a9-7ad9-b664-d35dcec77dc4" xlink:href="nmrk-20260630.xsd#nmrk_MortgageServicingRightsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_nmrk_MortgageServicingRightsTable_019e4774-a5a9-7ad9-b664-d35dcec77dc4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4774-a5a9-7eec-a318-68b740c88780" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nmrk_MortgageServicingRightsTable_019e4774-a5a9-7ad9-b664-d35dcec77dc4" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4774-a5a9-7eec-a318-68b740c88780" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a5a9-7eec-a318-68b740c88780_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a5a9-7eec-a318-68b740c88780" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a5a9-7eec-a318-68b740c88780_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a5a9-7d82-8fa9-f6144ba2c5b6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a5a9-7eec-a318-68b740c88780" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a5a9-7d82-8fa9-f6144ba2c5b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PrimaryServicingPortfolioMember_019e4774-a5a9-7159-80ad-37a8c6323398" xlink:href="nmrk-20260630.xsd#nmrk_PrimaryServicingPortfolioMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a5a9-7d82-8fa9-f6144ba2c5b6" xlink:to="loc_nmrk_PrimaryServicingPortfolioMember_019e4774-a5a9-7159-80ad-37a8c6323398" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedServicingPortfolioLoansWithMortgageServicingRightsMember_019e4774-a5a9-76b0-91c1-85fbe538f11a" xlink:href="nmrk-20260630.xsd#nmrk_LimitedServicingPortfolioLoansWithMortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a5a9-7d82-8fa9-f6144ba2c5b6" xlink:to="loc_nmrk_LimitedServicingPortfolioLoansWithMortgageServicingRightsMember_019e4774-a5a9-76b0-91c1-85fbe538f11a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7166-8a92-550653cc6600" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nmrk_MortgageServicingRightsTable_019e4774-a5a9-7ad9-b664-d35dcec77dc4" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7166-8a92-550653cc6600" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7166-8a92-550653cc6600_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7166-8a92-550653cc6600" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7166-8a92-550653cc6600_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7382-a38e-fe82f9a597e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_019e4774-a5a9-7166-8a92-550653cc6600" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7382-a38e-fe82f9a597e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MortgageServicingRightsMember_019e4774-a5a9-7044-90db-f99cdfb0c920" xlink:href="nmrk-20260630.xsd#nmrk_MortgageServicingRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_019e4774-a5a9-7382-a38e-fe82f9a597e3" xlink:to="loc_nmrk_MortgageServicingRightsMember_019e4774-a5a9-7044-90db-f99cdfb0c920" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a5a9-7c36-a36c-b9b5ccbace3d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nmrk_MortgageServicingRightsTable_019e4774-a5a9-7ad9-b664-d35dcec77dc4" xlink:to="loc_srt_RangeAxis_019e4774-a5a9-7c36-a36c-b9b5ccbace3d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a5a9-7c36-a36c-b9b5ccbace3d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a5a9-7c36-a36c-b9b5ccbace3d" xlink:to="loc_srt_RangeMember_019e4774-a5a9-7c36-a36c-b9b5ccbace3d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a5a9-7063-93cd-1dcda79e0632" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a5a9-7c36-a36c-b9b5ccbace3d" xlink:to="loc_srt_RangeMember_019e4774-a5a9-7063-93cd-1dcda79e0632" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a5a9-7b55-9f8d-eb5256792061" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a5a9-7063-93cd-1dcda79e0632" xlink:to="loc_srt_MinimumMember_019e4774-a5a9-7b55-9f8d-eb5256792061" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a5a9-7dfd-b3f1-8fee3dfbe03d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a5a9-7063-93cd-1dcda79e0632" xlink:to="loc_srt_MaximumMember_019e4774-a5a9-7dfd-b3f1-8fee3dfbe03d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019e4774-a5a9-702f-9d88-cd6b9deafdd6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nmrk_MortgageServicingRightsTable_019e4774-a5a9-7ad9-b664-d35dcec77dc4" xlink:to="loc_us-gaap_VariableRateAxis_019e4774-a5a9-702f-9d88-cd6b9deafdd6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019e4774-a5a9-702f-9d88-cd6b9deafdd6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019e4774-a5a9-702f-9d88-cd6b9deafdd6" xlink:to="loc_us-gaap_VariableRateDomain_019e4774-a5a9-702f-9d88-cd6b9deafdd6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019e4774-a5a9-7219-afe8-f5ed9259ac9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019e4774-a5a9-702f-9d88-cd6b9deafdd6" xlink:to="loc_us-gaap_VariableRateDomain_019e4774-a5a9-7219-afe8-f5ed9259ac9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_DiscountRateOneMember_019e4774-a5a9-7073-baeb-b850d2cb1aa3" xlink:href="nmrk-20260630.xsd#nmrk_DiscountRateOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e4774-a5a9-7219-afe8-f5ed9259ac9f" xlink:to="loc_nmrk_DiscountRateOneMember_019e4774-a5a9-7073-baeb-b850d2cb1aa3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_DiscountRateTwoMember_019e4774-a5a9-70bc-803f-1239249fd171" xlink:href="nmrk-20260630.xsd#nmrk_DiscountRateTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e4774-a5a9-7219-afe8-f5ed9259ac9f" xlink:to="loc_nmrk_DiscountRateTwoMember_019e4774-a5a9-70bc-803f-1239249fd171" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAsset_019e4774-a5a9-7f83-9d11-f3e4edd0f7ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_us-gaap_ServicingAsset_019e4774-a5a9-7f83-9d11-f3e4edd0f7ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_SpecialServicingPortfolio_019e4774-a5a9-73c3-a8e3-80c52c7ca9cf" xlink:href="nmrk-20260630.xsd#nmrk_SpecialServicingPortfolio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_nmrk_SpecialServicingPortfolio_019e4774-a5a9-73c3-a8e3-80c52c7ca9cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValueAmount_019e4774-a5a9-75dc-9046-dacca1e1144d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtFairValueAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_us-gaap_ServicingAssetAtFairValueAmount_019e4774-a5a9-75dc-9046-dacca1e1144d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate_019e4774-a5a9-76d8-aaed-9314a019c4ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_us-gaap_ServicingAssetsAndServicingLiabilitiesAtFairValueAssumptionsUsedToEstimateFairValueDiscountRate_019e4774-a5a9-76d8-aaed-9314a019c4ff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PercentageOfIncreaseInDiscountRateOfServicingRights_019e4774-a5a9-7ad4-94ee-66153f918c50" xlink:href="nmrk-20260630.xsd#nmrk_PercentageOfIncreaseInDiscountRateOfServicingRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_nmrk_PercentageOfIncreaseInDiscountRateOfServicingRights_019e4774-a5a9-7ad4-94ee-66153f918c50" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease_019e4774-a5a9-7020-8483-e2de23614361" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_MortgageServicingRightsLineItems_019e4774-a5a9-7e89-b7fa-9f5c985c8919" xlink:to="loc_us-gaap_ServicingAssetAtFairValuePeriodIncreaseDecrease_019e4774-a5a9-7020-8483-e2de23614361" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/GoodwillandOtherIntangibleAssetsNetScheduleofComponentsofOtherIntangibleAssetsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#GoodwillandOtherIntangibleAssetsNetScheduleofComponentsofOtherIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/GoodwillandOtherIntangibleAssetsNetScheduleofComponentsofOtherIntangibleAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:href="nmrk-20260630.xsd#nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassTable_019e4774-a5a9-7ae0-bc53-7732ebc616a5" xlink:href="nmrk-20260630.xsd#nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassTable_019e4774-a5a9-7ae0-bc53-7732ebc616a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7f1b-b997-e652438e8a5c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassTable_019e4774-a5a9-7ae0-bc53-7732ebc616a5" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7f1b-b997-e652438e8a5c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7f1b-b997-e652438e8a5c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7f1b-b997-e652438e8a5c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7f1b-b997-e652438e8a5c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7268-bb67-dd883fcbd9fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7f1b-b997-e652438e8a5c" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7268-bb67-dd883fcbd9fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_019e4774-a5a9-7bb7-8619-40f06da14147" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7268-bb67-dd883fcbd9fd" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_019e4774-a5a9-7bb7-8619-40f06da14147" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_019e4774-a5a9-7438-ae75-7a7c743f0de1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7268-bb67-dd883fcbd9fd" xlink:to="loc_us-gaap_LicensingAgreementsMember_019e4774-a5a9-7438-ae75-7a7c743f0de1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7fe8-a2cb-6b32503f858a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassTable_019e4774-a5a9-7ae0-bc53-7732ebc616a5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7fe8-a2cb-6b32503f858a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7fe8-a2cb-6b32503f858a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7fe8-a2cb-6b32503f858a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-7fe8-a2cb-6b32503f858a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_019e4774-a5a9-7fe8-a2cb-6b32503f858a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_019e4774-a5a9-70e6-8906-22b45d7260ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:to="loc_us-gaap_CustomerContractsMember_019e4774-a5a9-70e6-8906-22b45d7260ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019e4774-a5a9-7765-a38b-1d551e0521ad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_019e4774-a5a9-7765-a38b-1d551e0521ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_019e4774-a5a9-768a-9b29-30327a9af7cd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_019e4774-a5a9-768a-9b29-30327a9af7cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_019e4774-a5a9-751b-9af0-358677949318" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_019e4774-a5a9-751b-9af0-358677949318" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_019e4774-a5a9-7106-935f-dbfbb8850173" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_019e4774-a5a9-7106-935f-dbfbb8850173" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherIntangibleAssetsMember_019e4774-a5a9-7f04-9c06-8200cf7d936b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_019e4774-a5a9-78a0-9cc4-d2600fb35b8a" xlink:to="loc_us-gaap_OtherIntangibleAssetsMember_019e4774-a5a9-7f04-9c06-8200cf7d936b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_019e4774-a5a9-7bc6-bf60-c8864b25bf07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_019e4774-a5a9-7bc6-bf60-c8864b25bf07" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e4774-a5a9-759f-9f17-ce6a14fe9753" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_019e4774-a5a9-759f-9f17-ce6a14fe9753" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e4774-a5a9-789d-ac42-d0e5179b77e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_019e4774-a5a9-789d-ac42-d0e5179b77e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e4774-a5a9-7209-ae36-4f8553c01052" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_019e4774-a5a9-7209-ae36-4f8553c01052" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_019e4774-a5a9-7625-bb15-cfca7e60b9ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_019e4774-a5a9-7625-bb15-cfca7e60b9ff" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_019e4774-a5a9-7aec-910b-38587770f4e7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_019e4774-a5a9-7aec-910b-38587770f4e7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e4774-a5a9-7330-9924-2211a68e8d31" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_ScheduleOfAcquiredFiniteAndIndefiniteLivedIntangibleAssetByMajorClassLineItems_019e4774-a5a9-71f0-b30c-60c3971c5429" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_019e4774-a5a9-7330-9924-2211a68e8d31" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FixedAssetsNetScheduleofComponentsofFixedAssetsNetDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FixedAssetsNetScheduleofComponentsofFixedAssetsNetDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FixedAssetsNetScheduleofComponentsofFixedAssetsNetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-78e8-9317-07698b9b6a25" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019e4774-a5a9-7806-a2ac-d0e1674c0ba9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-78e8-9317-07698b9b6a25" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019e4774-a5a9-7806-a2ac-d0e1674c0ba9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7a7d-b535-d52502b94a9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019e4774-a5a9-7806-a2ac-d0e1674c0ba9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7a7d-b535-d52502b94a9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7a7d-b535-d52502b94a9f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7a7d-b535-d52502b94a9f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7a7d-b535-d52502b94a9f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-70bb-b16d-a112d0e62855" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7a7d-b535-d52502b94a9f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-70bb-b16d-a112d0e62855" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LeaseHoldImprovementsAndOtherFixedAssetsMember_019e4774-a5a9-773e-b139-cb00a88d5e58" xlink:href="nmrk-20260630.xsd#nmrk_LeaseHoldImprovementsAndOtherFixedAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-70bb-b16d-a112d0e62855" xlink:to="loc_nmrk_LeaseHoldImprovementsAndOtherFixedAssetsMember_019e4774-a5a9-773e-b139-cb00a88d5e58" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_019e4774-a5a9-763e-9cff-db74d0be8ed3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-70bb-b16d-a112d0e62855" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_019e4774-a5a9-763e-9cff-db74d0be8ed3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComputerEquipmentMember_019e4774-a5a9-78a2-a845-3453eaf8b798" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ComputerEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-70bb-b16d-a112d0e62855" xlink:to="loc_us-gaap_ComputerEquipmentMember_019e4774-a5a9-78a2-a845-3453eaf8b798" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_019e4774-a5a9-7d36-b63b-ca7cc952ce2e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-78e8-9317-07698b9b6a25" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_019e4774-a5a9-7d36-b63b-ca7cc952ce2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019e4774-a5a9-7388-a020-045064ab47ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-78e8-9317-07698b9b6a25" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_019e4774-a5a9-7388-a020-045064ab47ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_019e4774-a5a9-769d-adb0-2ee045bde972" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-78e8-9317-07698b9b6a25" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_019e4774-a5a9-769d-adb0-2ee045bde972" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FixedAssetsNetNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FixedAssetsNetNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FixedAssetsNetNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-7ef2-9223-aac5a6648095" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019e4774-a5a9-723a-8c2d-f340e154ba37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-7ef2-9223-aac5a6648095" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019e4774-a5a9-723a-8c2d-f340e154ba37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7f33-b5d3-7832fa7e654d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_019e4774-a5a9-723a-8c2d-f340e154ba37" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7f33-b5d3-7832fa7e654d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7f33-b5d3-7832fa7e654d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7f33-b5d3-7832fa7e654d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7f33-b5d3-7832fa7e654d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7a84-8b48-e2bbcbbb39f6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_019e4774-a5a9-7f33-b5d3-7832fa7e654d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7a84-8b48-e2bbcbbb39f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_019e4774-a5a9-7265-8197-819b07ef8b69" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_019e4774-a5a9-7a84-8b48-e2bbcbbb39f6" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_019e4774-a5a9-7265-8197-819b07ef8b69" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Depreciation_019e4774-a5a9-7aff-8ccc-cc6b816ca5aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Depreciation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-7ef2-9223-aac5a6648095" xlink:to="loc_us-gaap_Depreciation_019e4774-a5a9-7aff-8ccc-cc6b816ca5aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_019e4774-a5a9-756a-a1cb-4f7e7cc33690" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfLongLivedAssetsHeldForUse"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-7ef2-9223-aac5a6648095" xlink:to="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_019e4774-a5a9-756a-a1cb-4f7e7cc33690" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ImpairmentLongLivedAssetHeldForUseStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-76e4-90fa-5ad5af4f12ec" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentLongLivedAssetHeldForUseStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ImpairmentOfLongLivedAssetsHeldForUse_019e4774-a5a9-756a-a1cb-4f7e7cc33690" xlink:to="loc_us-gaap_ImpairmentLongLivedAssetHeldForUseStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_019e4774-a5a9-76e4-90fa-5ad5af4f12ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentAdditions_019efbc9-0ebb-757c-94b9-d5a34d86d80a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-7ef2-9223-aac5a6648095" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentAdditions_019efbc9-0ebb-757c-94b9-d5a34d86d80a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentForAmortization_019efbc9-0ebb-7d79-a442-4886868aa487" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentForAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_019e4774-a5a9-7ef2-9223-aac5a6648095" xlink:to="loc_us-gaap_AdjustmentForAmortization_019efbc9-0ebb-7d79-a442-4886868aa487" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/LeasesNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#LeasesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/LeasesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_019e4774-a5a9-7a76-a3a0-f2937ea0b179" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_019e4774-a5a9-7a76-a3a0-f2937ea0b179" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a5a9-7ca9-bd0e-06ef7324e4cf" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019e4774-a5a9-7a76-a3a0-f2937ea0b179" xlink:to="loc_srt_RangeAxis_019e4774-a5a9-7ca9-bd0e-06ef7324e4cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a5a9-7ca9-bd0e-06ef7324e4cf_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a5a9-7ca9-bd0e-06ef7324e4cf" xlink:to="loc_srt_RangeMember_019e4774-a5a9-7ca9-bd0e-06ef7324e4cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a5a9-7e13-923c-bae1efc2568f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a5a9-7ca9-bd0e-06ef7324e4cf" xlink:to="loc_srt_RangeMember_019e4774-a5a9-7e13-923c-bae1efc2568f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a5a9-77c2-8e52-101e6a856fc1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a5a9-7e13-923c-bae1efc2568f" xlink:to="loc_srt_MinimumMember_019e4774-a5a9-77c2-8e52-101e6a856fc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a5a9-7efc-bc40-109991a39e12" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a5a9-7e13-923c-bae1efc2568f" xlink:to="loc_srt_MaximumMember_019e4774-a5a9-7efc-bc40-109991a39e12" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_019e4774-a5a9-7785-8351-4a237bdb4e20" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_019e4774-a5a9-7a76-a3a0-f2937ea0b179" xlink:to="loc_srt_ProductOrServiceAxis_019e4774-a5a9-7785-8351-4a237bdb4e20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7785-8351-4a237bdb4e20_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a9-7785-8351-4a237bdb4e20" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7785-8351-4a237bdb4e20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7301-ad91-7da5b3b225b4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_019e4774-a5a9-7785-8351-4a237bdb4e20" xlink:to="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7301-ad91-7da5b3b225b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ManagementServicesServicingFeesAndOtherMember_019e4774-a5a9-7714-acf7-1022a366900c" xlink:href="nmrk-20260630.xsd#nmrk_ManagementServicesServicingFeesAndOtherMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_019e4774-a5a9-7301-ad91-7da5b3b225b4" xlink:to="loc_nmrk_ManagementServicesServicingFeesAndOtherMember_019e4774-a5a9-7714-acf7-1022a366900c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_019e4774-a5a9-7a73-aa58-915bb05750f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_019e4774-a5a9-7a73-aa58-915bb05750f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_019e4774-a5a9-7c79-a256-a4a76b741ac2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_019e4774-a5a9-7c79-a256-a4a76b741ac2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OperatingLeaseLiabilityIncludingSubleaseReceivables_019e4774-a5a9-7978-b530-15899f014a7b" xlink:href="nmrk-20260630.xsd#nmrk_OperatingLeaseLiabilityIncludingSubleaseReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_nmrk_OperatingLeaseLiabilityIncludingSubleaseReceivables_019e4774-a5a9-7978-b530-15899f014a7b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_019e4774-a5a9-7d15-b018-edf094e61f57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseLiability_019e4774-a5a9-7d15-b018-edf094e61f57" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OperatingLeaseFutureContractedRevenuesAndSubleaseIncome_019e4774-a5a9-7a8f-9e4f-1687c26a7c09" xlink:href="nmrk-20260630.xsd#nmrk_OperatingLeaseFutureContractedRevenuesAndSubleaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_nmrk_OperatingLeaseFutureContractedRevenuesAndSubleaseIncome_019e4774-a5a9-7a8f-9e4f-1687c26a7c09" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseCost_019e4774-a5a9-7f57-b4ae-13452e25ae8a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseCost_019e4774-a5a9-7f57-b4ae-13452e25ae8a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeasePayments_019e4774-a5a9-7228-8590-07395a393bd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeasePayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeasePayments_019e4774-a5a9-7228-8590-07395a393bd8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermLeaseCost_019e4774-a5a9-7c68-87cb-f0c09d5f6e55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermLeaseCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_ShortTermLeaseCost_019e4774-a5a9-7c68-87cb-f0c09d5f6e55" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubleaseIncome_019e4774-a5a9-75ed-92e7-2ebf4d7961d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubleaseIncome"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_SubleaseIncome_019e4774-a5a9-75ed-92e7-2ebf4d7961d3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseImpairmentLoss_019e4774-a5a9-748e-92de-250593e4d255" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseImpairmentLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseImpairmentLoss_019e4774-a5a9-748e-92de-250593e4d255" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_019e4774-a5a9-7bbc-a790-c7f9295761bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_019e4774-a5a9-7bbc-a790-c7f9295761bd" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_019e4774-a5a9-79b5-9396-aa937d50171a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_019e4774-a5a9-79b5-9396-aa937d50171a" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e4774-a5a9-7545-9fc7-199fb750165e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_019e4774-a5a9-7545-9fc7-199fb750165e" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_019e4774-a5a9-7365-8071-d374b25b58fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_019e4774-a5a9-7365-8071-d374b25b58fa" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_019e4774-a5a9-7b5f-8a1b-0682f367e09a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_019e4774-a5a9-7b5f-8a1b-0682f367e09a" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e4774-a5a9-76b4-bba8-a2c6f9a64f43" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_019e4774-a5a9-76b4-bba8-a2c6f9a64f43" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LeaseCost_019e4774-a5a9-7655-942b-55204205cff5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LeaseCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_019e4774-a5a9-7e4e-a488-0757c74cd010" xlink:to="loc_us-gaap_LeaseCost_019e4774-a5a9-7655-942b-55204205cff5" xlink:type="arc" order="16"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/WarehouseFacilitiesCollateralizedbyUSGovernmentSponsoredEnterprisesDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#WarehouseFacilitiesCollateralizedbyUSGovernmentSponsoredEnterprisesDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/WarehouseFacilitiesCollateralizedbyUSGovernmentSponsoredEnterprisesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesFinancingTransactionLineItems_019e4774-a5a9-72c6-8122-ae5e7f6a714a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuritiesFinancingTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuritiesFinancingTransactionTable_019e4774-a5a9-7b67-bab2-cf09e8c5de81" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuritiesFinancingTransactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionLineItems_019e4774-a5a9-72c6-8122-ae5e7f6a714a" xlink:to="loc_us-gaap_SecuritiesFinancingTransactionTable_019e4774-a5a9-7b67-bab2-cf09e8c5de81" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-759e-b98f-112b39bca4a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionTable_019e4774-a5a9-7b67-bab2-cf09e8c5de81" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-759e-b98f-112b39bca4a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-759e-b98f-112b39bca4a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-759e-b98f-112b39bca4a4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-759e-b98f-112b39bca4a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7aef-bd08-5189e3fea4a3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-759e-b98f-112b39bca4a4" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7aef-bd08-5189e3fea4a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_WarehouseFacilityDueMayFourTwoThousandTwentySevenMember_019ec8e9-0fc8-7fee-b316-0c3e0f06c5e5" xlink:href="nmrk-20260630.xsd#nmrk_WarehouseFacilityDueMayFourTwoThousandTwentySevenMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7aef-bd08-5189e3fea4a3" xlink:to="loc_nmrk_WarehouseFacilityDueMayFourTwoThousandTwentySevenMember_019ec8e9-0fc8-7fee-b316-0c3e0f06c5e5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_WarehouseFacilityDueSeptemberTwentyFiveTwoThousandTwentySixMember_019e4774-a5a9-71ce-abc3-be62089235b0" xlink:href="nmrk-20260630.xsd#nmrk_WarehouseFacilityDueSeptemberTwentyFiveTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7aef-bd08-5189e3fea4a3" xlink:to="loc_nmrk_WarehouseFacilityDueSeptemberTwentyFiveTwoThousandTwentySixMember_019e4774-a5a9-71ce-abc3-be62089235b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_WarehouseFacilityDueOctoberFourTwoThousandTwentySixMember_019e4774-a5a9-7c0c-ac63-ae4a6716072b" xlink:href="nmrk-20260630.xsd#nmrk_WarehouseFacilityDueOctoberFourTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7aef-bd08-5189e3fea4a3" xlink:to="loc_nmrk_WarehouseFacilityDueOctoberFourTwoThousandTwentySixMember_019e4774-a5a9-7c0c-ac63-ae4a6716072b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FannieMaeRepurchaseAgreementOpenMaturityMember_019e4774-a5a9-7f3b-b920-1268bc2b947f" xlink:href="nmrk-20260630.xsd#nmrk_FannieMaeRepurchaseAgreementOpenMaturityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7aef-bd08-5189e3fea4a3" xlink:to="loc_nmrk_FannieMaeRepurchaseAgreementOpenMaturityMember_019e4774-a5a9-7f3b-b920-1268bc2b947f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7b5f-a198-702146c5e988" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionTable_019e4774-a5a9-7b67-bab2-cf09e8c5de81" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7b5f-a198-702146c5e988" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7b5f-a198-702146c5e988_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7b5f-a198-702146c5e988" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7b5f-a198-702146c5e988_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-70cf-8da9-4f8b69ba0ce1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7b5f-a198-702146c5e988" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-70cf-8da9-4f8b69ba0ce1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CommittedLinesMember_019e4774-a5a9-7caa-98df-0903841ccc73" xlink:href="nmrk-20260630.xsd#nmrk_CommittedLinesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-70cf-8da9-4f8b69ba0ce1" xlink:to="loc_nmrk_CommittedLinesMember_019e4774-a5a9-7caa-98df-0903841ccc73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_UncommittedLinesMember_019e4774-a5a9-7d0c-8dca-17c114876c29" xlink:href="nmrk-20260630.xsd#nmrk_UncommittedLinesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-70cf-8da9-4f8b69ba0ce1" xlink:to="loc_nmrk_UncommittedLinesMember_019e4774-a5a9-7d0c-8dca-17c114876c29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_019e4774-a5a9-79c2-955d-74d2f02e2f78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionLineItems_019e4774-a5a9-72c6-8122-ae5e7f6a714a" xlink:to="loc_us-gaap_LineOfCreditFacilityCapacityAvailableForSpecificPurposeOtherThanForTradePurchases_019e4774-a5a9-79c2-955d-74d2f02e2f78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarehouseAgreementBorrowings_019e4774-a5a9-7d31-862b-99fa8a9b25e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarehouseAgreementBorrowings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionLineItems_019e4774-a5a9-72c6-8122-ae5e7f6a714a" xlink:to="loc_us-gaap_WarehouseAgreementBorrowings_019e4774-a5a9-7d31-862b-99fa8a9b25e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a5a9-7670-b5bd-b72412978755" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionLineItems_019e4774-a5a9-72c6-8122-ae5e7f6a714a" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a5a9-7670-b5bd-b72412978755" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet_019e4774-a5a9-71e8-8c6e-06776b338dda" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SecuritiesFinancingTransactionLineItems_019e4774-a5a9-72c6-8122-ae5e7f6a714a" xlink:to="loc_us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet_019e4774-a5a9-71e8-8c6e-06776b338dda" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtScheduleofDebtDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtScheduleofDebtDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtScheduleofDebtDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a5a9-7b71-8636-d216345500f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a5a9-7696-a643-c70834dc8cc5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a5a9-7b71-8636-d216345500f3" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a5a9-7696-a643-c70834dc8cc5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-7540-aa1a-812981d22f50" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a5a9-7696-a643-c70834dc8cc5" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-7540-aa1a-812981d22f50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7540-aa1a-812981d22f50_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-7540-aa1a-812981d22f50" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-7540-aa1a-812981d22f50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-71e9-ac6f-e9baef03d48a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a5a9-7540-aa1a-812981d22f50" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-71e9-ac6f-e9baef03d48a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a5a9-77cb-b0ef-d5f04449d089" xlink:href="nmrk-20260630.xsd#nmrk_A7.500SeniorNotesDueJanuary122029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a5a9-71e9-ac6f-e9baef03d48a" xlink:to="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a5a9-77cb-b0ef-d5f04449d089" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a5a9-7a60-98e3-6c9bcb37a758" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a5a9-7696-a643-c70834dc8cc5" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a5a9-7a60-98e3-6c9bcb37a758" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a5a9-7a60-98e3-6c9bcb37a758_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a5a9-7a60-98e3-6c9bcb37a758" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a5a9-7a60-98e3-6c9bcb37a758_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a5a9-7bb1-a827-2a2d2f8d6e80" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a5a9-7a60-98e3-6c9bcb37a758" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a5a9-7bb1-a827-2a2d2f8d6e80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e4774-a5a9-71ec-a501-f89bdfcbada7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a5a9-7bb1-a827-2a2d2f8d6e80" xlink:to="loc_us-gaap_SeniorNotesMember_019e4774-a5a9-71ec-a501-f89bdfcbada7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4774-a5a9-70da-8dec-5dd707fbd2cc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a5a9-7bb1-a827-2a2d2f8d6e80" xlink:to="loc_us-gaap_LineOfCreditMember_019e4774-a5a9-70da-8dec-5dd707fbd2cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7804-afa0-a5ada991f7c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a5a9-7696-a643-c70834dc8cc5" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7804-afa0-a5ada991f7c6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7804-afa0-a5ada991f7c6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7804-afa0-a5ada991f7c6" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7804-afa0-a5ada991f7c6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7fad-b4a5-07d5670eeb65" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a5a9-7804-afa0-a5ada991f7c6" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7fad-b4a5-07d5670eeb65" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a5a9-708e-9aec-5d6f1464e039" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a5a9-7fad-b4a5-07d5670eeb65" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a5a9-708e-9aec-5d6f1464e039" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a5a9-726b-bede-5f596ee19cd9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a5a9-7b71-8636-d216345500f3" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a5a9-726b-bede-5f596ee19cd9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_019e4774-a5a9-7a02-9a78-cca34d081cd5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a5a9-7b71-8636-d216345500f3" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_019e4774-a5a9-7a02-9a78-cca34d081cd5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e4774-a5a9-7ece-b25a-5f2ce4a9a711" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a5a9-7b71-8636-d216345500f3" xlink:to="loc_us-gaap_LongTermDebt_019e4774-a5a9-7ece-b25a-5f2ce4a9a711" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtSeniorNotesDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtSeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtSeniorNotesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7aea-a440-a0d95df0b44f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-771f-8a25-e3ac8da7ef3a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7aea-a440-a0d95df0b44f" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-771f-8a25-e3ac8da7ef3a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7c7e-8ee3-bca59f84a74d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-771f-8a25-e3ac8da7ef3a" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7c7e-8ee3-bca59f84a74d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7c7e-8ee3-bca59f84a74d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7c7e-8ee3-bca59f84a74d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7c7e-8ee3-bca59f84a74d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7ae0-ab82-48a7d2072e16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7c7e-8ee3-bca59f84a74d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7ae0-ab82-48a7d2072e16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67c-7272-ab8a-bffe54a6165a" xlink:href="nmrk-20260630.xsd#nmrk_A7.500SeniorNotesDueJanuary122029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7ae0-ab82-48a7d2072e16" xlink:to="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67c-7272-ab8a-bffe54a6165a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-718d-b3ea-17d8c38fd106" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-771f-8a25-e3ac8da7ef3a" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-718d-b3ea-17d8c38fd106" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-718d-b3ea-17d8c38fd106_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-718d-b3ea-17d8c38fd106" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-718d-b3ea-17d8c38fd106_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7bb3-acb4-ee3dec51f6f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-718d-b3ea-17d8c38fd106" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7bb3-acb4-ee3dec51f6f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e4774-a67c-7e24-a419-3ca9e37938c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7bb3-acb4-ee3dec51f6f4" xlink:to="loc_us-gaap_SeniorNotesMember_019e4774-a67c-7e24-a419-3ca9e37938c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67c-7ded-b72c-5ba11d1b446f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-771f-8a25-e3ac8da7ef3a" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67c-7ded-b72c-5ba11d1b446f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67c-7ded-b72c-5ba11d1b446f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67c-7ded-b72c-5ba11d1b446f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67c-7ded-b72c-5ba11d1b446f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67c-746b-8ddc-cc2dae450e0f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67c-7ded-b72c-5ba11d1b446f" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67c-746b-8ddc-cc2dae450e0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e4774-a67c-7a3f-92fd-56b3c00cdcd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67c-746b-8ddc-cc2dae450e0f" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e4774-a67c-7a3f-92fd-56b3c00cdcd7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a67c-7524-b694-4a8fd955e56f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7aea-a440-a0d95df0b44f" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a67c-7524-b694-4a8fd955e56f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019e4774-a67c-7e0c-8141-e9265d91cefe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7aea-a440-a0d95df0b44f" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019e4774-a67c-7e0c-8141-e9265d91cefe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtFairValue_019e4774-a67c-7ac7-b636-19f9c39c60a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7aea-a440-a0d95df0b44f" xlink:to="loc_us-gaap_LongTermDebtFairValue_019e4774-a67c-7ac7-b636-19f9c39c60a1" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtScheduleofSeniorNotesCarryingAmountDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtScheduleofSeniorNotesCarryingAmountDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtScheduleofSeniorNotesCarryingAmountDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7b13-ac75-20bdba184675" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7e53-bb49-bd598299932e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7b13-ac75-20bdba184675" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7e53-bb49-bd598299932e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-74d6-bdb0-7d0ab38c7746" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7e53-bb49-bd598299932e" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-74d6-bdb0-7d0ab38c7746" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-74d6-bdb0-7d0ab38c7746_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-74d6-bdb0-7d0ab38c7746" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-74d6-bdb0-7d0ab38c7746_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-734e-b5d1-65fead98e7f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-74d6-bdb0-7d0ab38c7746" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-734e-b5d1-65fead98e7f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67c-7f0e-a4f5-20c0817ae18b" xlink:href="nmrk-20260630.xsd#nmrk_A7.500SeniorNotesDueJanuary122029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-734e-b5d1-65fead98e7f9" xlink:to="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67c-7f0e-a4f5-20c0817ae18b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-70f4-b842-1d7d02ade5a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7e53-bb49-bd598299932e" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-70f4-b842-1d7d02ade5a9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-70f4-b842-1d7d02ade5a9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-70f4-b842-1d7d02ade5a9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-70f4-b842-1d7d02ade5a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-702c-8cc8-61133daf1209" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-70f4-b842-1d7d02ade5a9" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-702c-8cc8-61133daf1209" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e4774-a67c-7aca-8919-7002353f904d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-702c-8cc8-61133daf1209" xlink:to="loc_us-gaap_SeniorNotesMember_019e4774-a67c-7aca-8919-7002353f904d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_019e4774-a67c-7cf5-a99e-3c369e89116a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7b13-ac75-20bdba184675" xlink:to="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_019e4774-a67c-7cf5-a99e-3c369e89116a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_019e4774-a67c-7b1c-9f29-28b233cf2fd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_019e4774-a67c-7cf5-a99e-3c369e89116a" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_019e4774-a67c-7b1c-9f29-28b233cf2fd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsNet_019e4774-a67c-78a3-82f8-bc7e2f9d3a44" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_019e4774-a67c-7cf5-a99e-3c369e89116a" xlink:to="loc_us-gaap_DeferredFinanceCostsNet_019e4774-a67c-78a3-82f8-bc7e2f9d3a44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e4774-a67c-774d-82ab-7d28b5599240" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SeniorLongtermNotesCurrentAndNoncurrentAbstract_019e4774-a67c-7cf5-a99e-3c369e89116a" xlink:to="loc_us-gaap_LongTermDebt_019e4774-a67c-774d-82ab-7d28b5599240" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtScheduleofSeniorNotesNetInterestExpenseDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtScheduleofSeniorNotesNetInterestExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtScheduleofSeniorNotesNetInterestExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-79e5-b320-c769c3517b74" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7336-9d9a-156610cda764" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-79e5-b320-c769c3517b74" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7336-9d9a-156610cda764" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7d34-ad2b-08a798694a8d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7336-9d9a-156610cda764" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7d34-ad2b-08a798694a8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7d34-ad2b-08a798694a8d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7d34-ad2b-08a798694a8d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7d34-ad2b-08a798694a8d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7a00-ba9f-177b51458131" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7d34-ad2b-08a798694a8d" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7a00-ba9f-177b51458131" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67c-75a4-8474-7b33e6d39c46" xlink:href="nmrk-20260630.xsd#nmrk_A7.500SeniorNotesDueJanuary122029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7a00-ba9f-177b51458131" xlink:to="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67c-75a4-8474-7b33e6d39c46" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7936-a972-48ceecb25be6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7336-9d9a-156610cda764" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7936-a972-48ceecb25be6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7936-a972-48ceecb25be6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7936-a972-48ceecb25be6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7936-a972-48ceecb25be6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7277-8ba6-6b34c9987705" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7936-a972-48ceecb25be6" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7277-8ba6-6b34c9987705" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e4774-a67c-770e-87e1-d4b7a24c908a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7277-8ba6-6b34c9987705" xlink:to="loc_us-gaap_SeniorNotesMember_019e4774-a67c-770e-87e1-d4b7a24c908a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4774-a67c-741e-a520-5d45c882707f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7277-8ba6-6b34c9987705" xlink:to="loc_us-gaap_LineOfCreditMember_019e4774-a67c-741e-a520-5d45c882707f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-77ac-9225-e7032891475c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7336-9d9a-156610cda764" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-77ac-9225-e7032891475c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-77ac-9225-e7032891475c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-77ac-9225-e7032891475c" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-77ac-9225-e7032891475c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-7b8e-8188-727160de1898" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-77ac-9225-e7032891475c" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-7b8e-8188-727160de1898" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67c-74d0-8552-50fa25169c37" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-7b8e-8188-727160de1898" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67c-74d0-8552-50fa25169c37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebtAbstract_019e4774-a67c-794f-aeba-915c1eeb17d1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebtAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-79e5-b320-c769c3517b74" xlink:to="loc_us-gaap_InterestExpenseDebtAbstract_019e4774-a67c-794f-aeba-915c1eeb17d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseLongTermDebt_019e4774-a67c-7fbd-bd4c-1431e1a550ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_019e4774-a67c-794f-aeba-915c1eeb17d1" xlink:to="loc_us-gaap_InterestExpenseLongTermDebt_019e4774-a67c-7fbd-bd4c-1431e1a550ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_019e4774-a67c-792e-a587-5d1199187e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_019e4774-a67c-794f-aeba-915c1eeb17d1" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_019e4774-a67c-792e-a587-5d1199187e4d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_019e4774-a67c-74f0-a8f8-df508af570bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_019e4774-a67c-794f-aeba-915c1eeb17d1" xlink:to="loc_us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_019e4774-a67c-74f0-a8f8-df508af570bf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_019e4774-a67c-7014-b95d-36968c0e0732" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InterestExpenseDebtAbstract_019e4774-a67c-794f-aeba-915c1eeb17d1" xlink:to="loc_us-gaap_InterestExpense_019e4774-a67c-7014-b95d-36968c0e0732" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtDebtRepurchaseProgramDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtDebtRepurchaseProgramDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtDebtRepurchaseProgramDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7970-9135-87e507174bde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-745e-b133-3285b580dff4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7970-9135-87e507174bde" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-745e-b133-3285b580dff4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7e84-9240-1ccf3107bc5a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-745e-b133-3285b580dff4" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7e84-9240-1ccf3107bc5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7e84-9240-1ccf3107bc5a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7e84-9240-1ccf3107bc5a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7e84-9240-1ccf3107bc5a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7159-9030-2146abf419a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7e84-9240-1ccf3107bc5a" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7159-9030-2146abf419a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_SixPointOneTwoFivePercentSeniorNotesMember_019e4774-a67c-7c0b-9659-efa439b941f7" xlink:href="nmrk-20260630.xsd#nmrk_SixPointOneTwoFivePercentSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7159-9030-2146abf419a1" xlink:to="loc_nmrk_SixPointOneTwoFivePercentSeniorNotesMember_019e4774-a67c-7c0b-9659-efa439b941f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-778e-b5e2-6d066451cd07" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-745e-b133-3285b580dff4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-778e-b5e2-6d066451cd07" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-778e-b5e2-6d066451cd07_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-778e-b5e2-6d066451cd07" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-778e-b5e2-6d066451cd07_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7f1d-b7f0-6992012a8fbc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-778e-b5e2-6d066451cd07" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7f1d-b7f0-6992012a8fbc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e4774-a67c-7169-97de-7c2b4cab64a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7f1d-b7f0-6992012a8fbc" xlink:to="loc_us-gaap_SeniorNotesMember_019e4774-a67c-7169-97de-7c2b4cab64a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_DebtInstrumentDebtRepurchaseProgramAuthorizedAmount_019e4774-a67c-75d7-813c-b7e049a6cb2a" xlink:href="nmrk-20260630.xsd#nmrk_DebtInstrumentDebtRepurchaseProgramAuthorizedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7970-9135-87e507174bde" xlink:to="loc_nmrk_DebtInstrumentDebtRepurchaseProgramAuthorizedAmount_019e4774-a67c-75d7-813c-b7e049a6cb2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_DebtInstrumentDebtRepurchaseProgramRemainingAuthorizedRepurchaseAmount_019e4774-a67c-7523-a613-4fbe8b915c4e" xlink:href="nmrk-20260630.xsd#nmrk_DebtInstrumentDebtRepurchaseProgramRemainingAuthorizedRepurchaseAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7970-9135-87e507174bde" xlink:to="loc_nmrk_DebtInstrumentDebtRepurchaseProgramRemainingAuthorizedRepurchaseAmount_019e4774-a67c-7523-a613-4fbe8b915c4e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtCreditFacilityDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtCreditFacilityDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtCreditFacilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-70c2-becb-658df6797a7b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-70c2-becb-658df6797a7b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-793c-9f97-042f4110dcfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-70c2-becb-658df6797a7b" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-793c-9f97-042f4110dcfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-793c-9f97-042f4110dcfe_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-793c-9f97-042f4110dcfe" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-793c-9f97-042f4110dcfe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-7da7-aafa-b73c6e9e3bf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-793c-9f97-042f4110dcfe" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-7da7-aafa-b73c6e9e3bf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67c-732f-b5b8-9b31f397b443" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-7da7-aafa-b73c6e9e3bf9" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67c-732f-b5b8-9b31f397b443" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7954-badd-17086e623d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-70c2-becb-658df6797a7b" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7954-badd-17086e623d3c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7954-badd-17086e623d3c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7954-badd-17086e623d3c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7954-badd-17086e623d3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-77b6-9b4a-25f7ec2dec49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7954-badd-17086e623d3c" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-77b6-9b4a-25f7ec2dec49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4774-a67c-7974-a9e5-57244b019fd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-77b6-9b4a-25f7ec2dec49" xlink:to="loc_us-gaap_LineOfCreditMember_019e4774-a67c-7974-a9e5-57244b019fd1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateAxis_019e4774-a67c-7f95-8698-58d373f3696d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-70c2-becb-658df6797a7b" xlink:to="loc_us-gaap_VariableRateAxis_019e4774-a67c-7f95-8698-58d373f3696d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019e4774-a67c-7f95-8698-58d373f3696d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_019e4774-a67c-7f95-8698-58d373f3696d" xlink:to="loc_us-gaap_VariableRateDomain_019e4774-a67c-7f95-8698-58d373f3696d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VariableRateDomain_019e4774-a67c-752d-99a1-63e0ea3527bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_019e4774-a67c-7f95-8698-58d373f3696d" xlink:to="loc_us-gaap_VariableRateDomain_019e4774-a67c-752d-99a1-63e0ea3527bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019e4774-a67c-7bc4-a7bf-49547b7baad1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FederalFundsEffectiveSwapRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e4774-a67c-752d-99a1-63e0ea3527bb" xlink:to="loc_us-gaap_FederalFundsEffectiveSwapRateMember_019e4774-a67c-7bc4-a7bf-49547b7baad1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019e4774-a67c-74c7-b6eb-3b2c36b03065" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SecuredOvernightFinancingRateSofrMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e4774-a67c-752d-99a1-63e0ea3527bb" xlink:to="loc_us-gaap_SecuredOvernightFinancingRateSofrMember_019e4774-a67c-74c7-b6eb-3b2c36b03065" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BaseRateMember_019e4774-a67c-7113-a397-f7999cfbbc99" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BaseRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_019e4774-a67c-752d-99a1-63e0ea3527bb" xlink:to="loc_us-gaap_BaseRateMember_019e4774-a67c-7113-a397-f7999cfbbc99" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a67c-787e-80e4-0798c44bc557" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-70c2-becb-658df6797a7b" xlink:to="loc_srt_RangeAxis_019e4774-a67c-787e-80e4-0798c44bc557" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67c-787e-80e4-0798c44bc557_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a67c-787e-80e4-0798c44bc557" xlink:to="loc_srt_RangeMember_019e4774-a67c-787e-80e4-0798c44bc557_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67c-70c2-a939-9f36e01d9821" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a67c-787e-80e4-0798c44bc557" xlink:to="loc_srt_RangeMember_019e4774-a67c-70c2-a939-9f36e01d9821" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a67c-76b8-8b53-186b951fd029" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67c-70c2-a939-9f36e01d9821" xlink:to="loc_srt_MinimumMember_019e4774-a67c-76b8-8b53-186b951fd029" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a67c-731a-a928-457981283188" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67c-70c2-a939-9f36e01d9821" xlink:to="loc_srt_MaximumMember_019e4774-a67c-731a-a928-457981283188" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_019e4774-a67c-7fd5-854f-172e05780c9c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67c-70c2-a939-9f36e01d9821" xlink:to="loc_srt_WeightedAverageMember_019e4774-a67c-7fd5-854f-172e05780c9c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4774-a67c-7279-9718-72075fc8ba24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4774-a67c-7279-9718-72075fc8ba24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtTerm_019e4774-a67c-72a0-abfb-6aee53e5b966" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_LongTermDebtTerm_019e4774-a67c-72a0-abfb-6aee53e5b966" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption_019f93a8-2ab1-77bc-8806-da9c1747b194" xlink:href="nmrk-20260630.xsd#nmrk_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_nmrk_LineOfCreditFacilityAccordionFeatureHigherBorrowingCapacityOption_019f93a8-2ab1-77bc-8806-da9c1747b194" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration_019e4774-a67c-73c0-aa09-ef883d02ff85" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_DebtInstrumentVariableInterestRateTypeExtensibleEnumeration_019e4774-a67c-73c0-aa09-ef883d02ff85" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a67c-7190-bfd7-7c915a26ffc4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a67c-7190-bfd7-7c915a26ffc4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_DebtInstrumentAdjustmentRate_019e4774-a67c-7021-aa25-ebbe59d61ffc" xlink:href="nmrk-20260630.xsd#nmrk_DebtInstrumentAdjustmentRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_nmrk_DebtInstrumentAdjustmentRate_019e4774-a67c-7021-aa25-ebbe59d61ffc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_019e4774-a67c-7941-bea3-850a7aad4126" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_LineOfCredit_019e4774-a67c-7941-bea3-850a7aad4126" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_019e4774-a67c-7621-9e90-331db5154029" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_019e4774-a67c-7621-9e90-331db5154029" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_019e4774-a67c-739c-8990-160b39b2fabf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_019e4774-a67c-739c-8990-160b39b2fabf" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_019e4774-a67c-76e4-9e78-74bc988d57be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-7653-89cd-4953fc7916f0" xlink:to="loc_us-gaap_RepaymentsOfLongTermLinesOfCredit_019e4774-a67c-76e4-9e78-74bc988d57be" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/DebtCantorCreditAgreementDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#DebtCantorCreditAgreementDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/DebtCantorCreditAgreementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-71f9-9374-fa94b7c59e9e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7a09-9fc3-e32987eedfdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-71f9-9374-fa94b7c59e9e" xlink:to="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7a09-9fc3-e32987eedfdd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-73cf-a2b5-1fd59e887158" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7a09-9fc3-e32987eedfdd" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-73cf-a2b5-1fd59e887158" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-73cf-a2b5-1fd59e887158_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-73cf-a2b5-1fd59e887158" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-73cf-a2b5-1fd59e887158_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-772f-bf89-8e2f14a2a87f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67c-73cf-a2b5-1fd59e887158" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-772f-bf89-8e2f14a2a87f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67c-7bbf-87d3-c832a5f5d4df" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a67c-772f-bf89-8e2f14a2a87f" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67c-7bbf-87d3-c832a5f5d4df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7dfb-b3b6-cf638112282c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7a09-9fc3-e32987eedfdd" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7dfb-b3b6-cf638112282c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7dfb-b3b6-cf638112282c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7dfb-b3b6-cf638112282c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7dfb-b3b6-cf638112282c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7341-a20c-5dac45c0c970" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67c-7dfb-b3b6-cf638112282c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7341-a20c-5dac45c0c970" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CantorCreditAgreementMember_019e4774-a67c-7478-b5af-0bc3bf8cae6b" xlink:href="nmrk-20260630.xsd#nmrk_CantorCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67c-7341-a20c-5dac45c0c970" xlink:to="loc_nmrk_CantorCreditAgreementMember_019e4774-a67c-7478-b5af-0bc3bf8cae6b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7777-96db-87b7c1a7e008" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_019e4774-a67c-7a09-9fc3-e32987eedfdd" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7777-96db-87b7c1a7e008" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7777-96db-87b7c1a7e008_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7777-96db-87b7c1a7e008" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7777-96db-87b7c1a7e008_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7c50-9efb-5fdb0d556255" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67c-7777-96db-87b7c1a7e008" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7c50-9efb-5fdb0d556255" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4774-a67c-75ae-aea2-1eb88585d963" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67c-7c50-9efb-5fdb0d556255" xlink:to="loc_us-gaap_LineOfCreditMember_019e4774-a67c-75ae-aea2-1eb88585d963" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4774-a67c-7c83-876e-493c25037471" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-71f9-9374-fa94b7c59e9e" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4774-a67c-7c83-876e-493c25037471" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a67c-79ab-98d7-77eb6d4a0376" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-71f9-9374-fa94b7c59e9e" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a67c-79ab-98d7-77eb6d4a0376" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e4774-a67c-74d8-9b62-b89e63b09a63" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_019e4774-a67c-71f9-9374-fa94b7c59e9e" xlink:to="loc_us-gaap_LongTermDebt_019e4774-a67c-74d8-9b62-b89e63b09a63" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FinancialGuaranteeLiabilityNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FinancialGuaranteeLiabilityNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FinancialGuaranteeLiabilityNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019e4774-a67d-7cc2-8c03-cb599cab8102" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfGuaranteeObligationsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019e4774-a67d-7cc2-8c03-cb599cab8102" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a67d-7525-9ed6-854e329be57f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019e4774-a67d-7cc2-8c03-cb599cab8102" xlink:to="loc_srt_RangeAxis_019e4774-a67d-7525-9ed6-854e329be57f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-7525-9ed6-854e329be57f_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7525-9ed6-854e329be57f" xlink:to="loc_srt_RangeMember_019e4774-a67d-7525-9ed6-854e329be57f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-72a9-90f3-e5d0d13f6b5b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7525-9ed6-854e329be57f" xlink:to="loc_srt_RangeMember_019e4774-a67d-72a9-90f3-e5d0d13f6b5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a67d-70ff-9243-b063b899d439" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-72a9-90f3-e5d0d13f6b5b" xlink:to="loc_srt_MaximumMember_019e4774-a67d-70ff-9243-b063b899d439" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7267-8ce4-6b01e1b16f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019e4774-a67d-7cc2-8c03-cb599cab8102" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7267-8ce4-6b01e1b16f7f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7267-8ce4-6b01e1b16f7f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7267-8ce4-6b01e1b16f7f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7267-8ce4-6b01e1b16f7f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7096-87e1-3893bbf21b9d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7267-8ce4-6b01e1b16f7f" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7096-87e1-3893bbf21b9d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FannieMaeDUSOrFreddieTargetedAffordableHousingLoansMember_019e4774-a67d-7abf-babd-fc22664776ff" xlink:href="nmrk-20260630.xsd#nmrk_FannieMaeDUSOrFreddieTargetedAffordableHousingLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7096-87e1-3893bbf21b9d" xlink:to="loc_nmrk_FannieMaeDUSOrFreddieTargetedAffordableHousingLoansMember_019e4774-a67d-7abf-babd-fc22664776ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsByNatureAxis_019e4774-a67d-77d9-88f4-b0bbc740e229" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsByNatureAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGuaranteeObligationsTable_019e4774-a67d-7cc2-8c03-cb599cab8102" xlink:to="loc_us-gaap_GuaranteeObligationsByNatureAxis_019e4774-a67d-77d9-88f4-b0bbc740e229" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_019e4774-a67d-77d9-88f4-b0bbc740e229_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_019e4774-a67d-77d9-88f4-b0bbc740e229" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_019e4774-a67d-77d9-88f4-b0bbc740e229_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GuaranteeObligationsNatureDomain_019e4774-a67d-7ef1-8d7d-78c07ddb5a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GuaranteeObligationsNatureDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GuaranteeObligationsByNatureAxis_019e4774-a67d-77d9-88f4-b0bbc740e229" xlink:to="loc_us-gaap_GuaranteeObligationsNatureDomain_019e4774-a67d-7ef1-8d7d-78c07ddb5a1e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_DelinquentLoanMember_019e4774-a67d-7a1b-a06f-76cb4295e26f" xlink:href="nmrk-20260630.xsd#nmrk_DelinquentLoanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_019e4774-a67d-7ef1-8d7d-78c07ddb5a1e" xlink:to="loc_nmrk_DelinquentLoanMember_019e4774-a67d-7a1b-a06f-76cb4295e26f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LoanForeclosureMember_019e4774-a67d-7dd5-81fc-60672e341aa9" xlink:href="nmrk-20260630.xsd#nmrk_LoanForeclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsNatureDomain_019e4774-a67d-7ef1-8d7d-78c07ddb5a1e" xlink:to="loc_nmrk_LoanForeclosureMember_019e4774-a67d-7dd5-81fc-60672e341aa9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PercentageOfContingentLiabilityOfActualLossesIncurredOnOutstandingLoans_019e4774-a67d-7963-967b-615d39bac3af" xlink:href="nmrk-20260630.xsd#nmrk_PercentageOfContingentLiabilityOfActualLossesIncurredOnOutstandingLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_PercentageOfContingentLiabilityOfActualLossesIncurredOnOutstandingLoans_019e4774-a67d-7963-967b-615d39bac3af" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FinancialGuaranteeLiabilityCreditRiskServiceLoans_019e4774-a67d-7168-bdf8-3675cbf79fb6" xlink:href="nmrk-20260630.xsd#nmrk_FinancialGuaranteeLiabilityCreditRiskServiceLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_FinancialGuaranteeLiabilityCreditRiskServiceLoans_019e4774-a67d-7168-bdf8-3675cbf79fb6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FinancialGuaranteeLiabilityMaximumPotentialLoss_019e4774-a67d-75a8-ab6a-0ec7bf3dceb3" xlink:href="nmrk-20260630.xsd#nmrk_FinancialGuaranteeLiabilityMaximumPotentialLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_FinancialGuaranteeLiabilityMaximumPotentialLoss_019e4774-a67d-75a8-ab6a-0ec7bf3dceb3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ProvisionReversalForRiskSharingObligations_019e4774-a67d-784f-be51-04fb03449cf5" xlink:href="nmrk-20260630.xsd#nmrk_ProvisionReversalForRiskSharingObligations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_ProvisionReversalForRiskSharingObligations_019e4774-a67d-784f-be51-04fb03449cf5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FinancialGuaranteeLiabilityDelinquencyThresholdPeriod_019e4774-a67d-7ed1-bea3-39c9f09bc1d2" xlink:href="nmrk-20260630.xsd#nmrk_FinancialGuaranteeLiabilityDelinquencyThresholdPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_FinancialGuaranteeLiabilityDelinquencyThresholdPeriod_019e4774-a67d-7ed1-bea3-39c9f09bc1d2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NumberOfLoans_019e4774-a67d-74f7-880b-f320b4e71536" xlink:href="nmrk-20260630.xsd#nmrk_NumberOfLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_NumberOfLoans_019e4774-a67d-74f7-880b-f320b4e71536" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_AdvancesForPrincipalAndInterest_019e4774-a67d-7e6a-82a9-79383801e158" xlink:href="nmrk-20260630.xsd#nmrk_AdvancesForPrincipalAndInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_AdvancesForPrincipalAndInterest_019e4774-a67d-7e6a-82a9-79383801e158" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LiquidationValueOfLoansOutstanding_019e4774-a67d-7174-83d3-df4930cb4f3a" xlink:href="nmrk-20260630.xsd#nmrk_LiquidationValueOfLoansOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GuaranteeObligationsLineItems_019e4774-a67d-79f3-95c1-ae6528b666bd" xlink:to="loc_nmrk_LiquidationValueOfLoansOutstanding_019e4774-a67d-7174-83d3-df4930cb4f3a" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/ConcentrationsofCreditRiskDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#ConcentrationsofCreditRiskDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/ConcentrationsofCreditRiskDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_019e4774-a67d-7ad6-a39c-b595693cdb0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTable_019e4774-a67d-7ae7-8f7c-83c715e598aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019e4774-a67d-7ad6-a39c-b595693cdb0b" xlink:to="loc_us-gaap_ConcentrationRiskTable_019e4774-a67d-7ae7-8f7c-83c715e598aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_019e4774-a67d-7e82-a6c2-674acbb9b4e8" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019e4774-a67d-7ae7-8f7c-83c715e598aa" xlink:to="loc_srt_StatementGeographicalAxis_019e4774-a67d-7e82-a6c2-674acbb9b4e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e4774-a67d-7e82-a6c2-674acbb9b4e8_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_019e4774-a67d-7e82-a6c2-674acbb9b4e8" xlink:to="loc_srt_SegmentGeographicalDomain_019e4774-a67d-7e82-a6c2-674acbb9b4e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_019e4774-a67d-7c85-ba06-8b75c2a7c2b5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_019e4774-a67d-7e82-a6c2-674acbb9b4e8" xlink:to="loc_srt_SegmentGeographicalDomain_019e4774-a67d-7c85-ba06-8b75c2a7c2b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_CA_019e4774-a67d-7096-97c7-dea022816494" xlink:href="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd#stpr_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4774-a67d-7c85-ba06-8b75c2a7c2b5" xlink:to="loc_stpr_CA_019e4774-a67d-7096-97c7-dea022816494" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_stpr_TX_019e4774-a67d-7ff0-a1cb-f82cafe582bd" xlink:href="https://xbrl.sec.gov/stpr/2026/stpr-2026.xsd#stpr_TX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_019e4774-a67d-7c85-ba06-8b75c2a7c2b5" xlink:to="loc_stpr_TX_019e4774-a67d-7ff0-a1cb-f82cafe582bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4774-a67d-7a4f-9584-bb17465366f4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019e4774-a67d-7ae7-8f7c-83c715e598aa" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4774-a67d-7a4f-9584-bb17465366f4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4774-a67d-7a4f-9584-bb17465366f4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4774-a67d-7a4f-9584-bb17465366f4" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4774-a67d-7a4f-9584-bb17465366f4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4774-a67d-77e8-aeba-9106307e75ee" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskBenchmarkDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_019e4774-a67d-7a4f-9584-bb17465366f4" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4774-a67d-77e8-aeba-9106307e75ee" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesTotalMember_019e4774-a67d-7f3b-9f0b-24a6008aa7d5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_019e4774-a67d-77e8-aeba-9106307e75ee" xlink:to="loc_us-gaap_LiabilitiesTotalMember_019e4774-a67d-7f3b-9f0b-24a6008aa7d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4774-a67d-748e-87ef-9c421cffb848" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_019e4774-a67d-7ae7-8f7c-83c715e598aa" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4774-a67d-748e-87ef-9c421cffb848" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e4774-a67d-748e-87ef-9c421cffb848_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4774-a67d-748e-87ef-9c421cffb848" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e4774-a67d-748e-87ef-9c421cffb848_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_019e4774-a67d-79b0-99be-25c33ebac8f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_019e4774-a67d-748e-87ef-9c421cffb848" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_019e4774-a67d-79b0-99be-25c33ebac8f2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditConcentrationRiskMember_019e4774-a67d-7309-a736-48323045e417" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditConcentrationRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_019e4774-a67d-79b0-99be-25c33ebac8f2" xlink:to="loc_us-gaap_CreditConcentrationRiskMember_019e4774-a67d-7309-a736-48323045e417" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_019e4774-a67d-7324-94e9-2659bbc910a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskPercentage1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019e4774-a67d-7ad6-a39c-b595693cdb0b" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_019e4774-a67d-7324-94e9-2659bbc910a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure_019e4774-a67d-782c-acfc-408be4bd1a33" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_019e4774-a67d-7ad6-a39c-b595693cdb0b" xlink:to="loc_us-gaap_ConcentrationRiskCreditRiskFinancialInstrumentMaximumExposure_019e4774-a67d-782c-acfc-408be4bd1a33" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesScheduleofFairValueHierarchyofFinancialAssetsandLiabilitiesunderUSGAAPGuidanceDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FairValueofFinancialAssetsandLiabilitiesScheduleofFairValueHierarchyofFinancialAssetsandLiabilitiesunderUSGAAPGuidanceDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesScheduleofFairValueHierarchyofFinancialAssetsandLiabilitiesunderUSGAAPGuidanceDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-79b2-a5c9-53ff3997642a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7bcf-85f2-69af47c8c47b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-79b2-a5c9-53ff3997642a" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7bcf-85f2-69af47c8c47b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7a6f-beaf-a6d17d7abfed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7bcf-85f2-69af47c8c47b" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7a6f-beaf-a6d17d7abfed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7a6f-beaf-a6d17d7abfed_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7a6f-beaf-a6d17d7abfed" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7a6f-beaf-a6d17d7abfed_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7624-b978-315484743fe8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7a6f-beaf-a6d17d7abfed" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7624-b978-315484743fe8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_019e4774-a67d-77d4-94d7-56dffae70127" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7624-b978-315484743fe8" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_019e4774-a67d-77d4-94d7-56dffae70127" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_019e4774-a67d-7d18-a34d-55e5e6c549a6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7624-b978-315484743fe8" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_019e4774-a67d-7d18-a34d-55e5e6c549a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e4774-a67d-7879-9b1b-d48c10ef5b71" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7624-b978-315484743fe8" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e4774-a67d-7879-9b1b-d48c10ef5b71" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7f74-b974-e78404c23fd4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7bcf-85f2-69af47c8c47b" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7f74-b974-e78404c23fd4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7f74-b974-e78404c23fd4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7f74-b974-e78404c23fd4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7f74-b974-e78404c23fd4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7a69-8ed7-0bd9148066bc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7f74-b974-e78404c23fd4" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7a69-8ed7-0bd9148066bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a67d-798c-8a95-b0bd1de02592" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7a69-8ed7-0bd9148066bc" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a67d-798c-8a95-b0bd1de02592" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_019e4774-a67d-7213-8852-07c7da1ff899" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForwardContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7a69-8ed7-0bd9148066bc" xlink:to="loc_us-gaap_ForwardContractsMember_019e4774-a67d-7213-8852-07c7da1ff899" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-7a74-a314-8a731920bb15" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7bcf-85f2-69af47c8c47b" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-7a74-a314-8a731920bb15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7a74-a314-8a731920bb15_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-7a74-a314-8a731920bb15" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7a74-a314-8a731920bb15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7e72-9129-528d5b9cafc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-7a74-a314-8a731920bb15" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7e72-9129-528d5b9cafc8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_019e4774-a67d-7ee1-bcdc-88defb67957f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7e72-9129-528d5b9cafc8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_019e4774-a67d-7ee1-bcdc-88defb67957f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019e4774-a67d-7fd4-954f-d496440fe5dc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-79b2-a5c9-53ff3997642a" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019e4774-a67d-7fd4-954f-d496440fe5dc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019e4774-a67d-7017-b5cb-71ff8137b973" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LoansHeldForSaleFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019e4774-a67d-7fd4-954f-d496440fe5dc" xlink:to="loc_us-gaap_LoansHeldForSaleFairValueDisclosure_019e4774-a67d-7017-b5cb-71ff8137b973" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_019e4774-a67d-7bf7-a481-f4b65986553c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019e4774-a67d-7fd4-954f-d496440fe5dc" xlink:to="loc_us-gaap_DerivativeAssets_019e4774-a67d-7bf7-a481-f4b65986553c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_019e4774-a67d-777c-9692-63d45b7f4819" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialAssetsBalanceSheetGroupingsAbstract_019e4774-a67d-7fd4-954f-d496440fe5dc" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_019e4774-a67d-777c-9692-63d45b7f4819" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019e4774-a67d-7ea3-8b49-ce6e8671ca33" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-79b2-a5c9-53ff3997642a" xlink:to="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019e4774-a67d-7ea3-8b49-ce6e8671ca33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_019e4774-a67d-7d86-a688-42a5727007aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019e4774-a67d-7ea3-8b49-ce6e8671ca33" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_019e4774-a67d-7d86-a688-42a5727007aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_019e4774-a67d-7249-9250-57b77d040d7c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019e4774-a67d-7ea3-8b49-ce6e8671ca33" xlink:to="loc_us-gaap_DerivativeLiabilities_019e4774-a67d-7249-9250-57b77d040d7c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesFairValueDisclosure_019e4774-a67d-7ac0-9992-7e1fb347f126" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancialInstrumentsFinancialLiabilitiesBalanceSheetGroupingsAbstract_019e4774-a67d-7ea3-8b49-ce6e8671ca33" xlink:to="loc_us-gaap_LiabilitiesFairValueDisclosure_019e4774-a67d-7ac0-9992-7e1fb347f126" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesScheduleofChangesinLevel3AssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FairValueofFinancialAssetsandLiabilitiesScheduleofChangesinLevel3AssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesScheduleofChangesinLevel3AssetsandLiabilitiesMeasuredatFairValueonRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019e4774-a67d-7fa5-bdfb-53f0026bcf1a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019e4774-a67d-7fa5-bdfb-53f0026bcf1a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-736d-83dc-ebb31a69ef13" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_019e4774-a67d-7fa5-bdfb-53f0026bcf1a" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-736d-83dc-ebb31a69ef13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-736d-83dc-ebb31a69ef13_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-736d-83dc-ebb31a69ef13" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-736d-83dc-ebb31a69ef13_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7611-8246-aaf67e37c41a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-736d-83dc-ebb31a69ef13" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7611-8246-aaf67e37c41a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ContingentConsiderationLiabilityMember_019e4774-a67d-7b2e-85bf-a13ca9b0f054" xlink:href="nmrk-20260630.xsd#nmrk_ContingentConsiderationLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7611-8246-aaf67e37c41a" xlink:to="loc_nmrk_ContingentConsiderationLiabilityMember_019e4774-a67d-7b2e-85bf-a13ca9b0f054" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a67d-7d60-b657-5b182f9933f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7611-8246-aaf67e37c41a" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a67d-7d60-b657-5b182f9933f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_019e4774-a67d-7783-9fea-70ced6ef8176" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForwardContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7611-8246-aaf67e37c41a" xlink:to="loc_us-gaap_ForwardContractsMember_019e4774-a67d-7783-9fea-70ced6ef8176" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7b46-8ecb-265648e661fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7b46-8ecb-265648e661fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019e4774-a67d-720a-b8a9-7eaa562de7bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7b46-8ecb-265648e661fa" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019e4774-a67d-720a-b8a9-7eaa562de7bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019e4774-a67d-799b-b348-36afed8df073" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7b46-8ecb-265648e661fa" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_019e4774-a67d-799b-b348-36afed8df073" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019e4774-a67d-721e-9240-79770a851a35" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7b46-8ecb-265648e661fa" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_019e4774-a67d-721e-9240-79770a851a35" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019e4774-a67d-76e6-8c00-26c276ba7805" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7b46-8ecb-265648e661fa" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_019e4774-a67d-76e6-8c00-26c276ba7805" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_019e4774-a67d-7c5f-b791-001a4c9b219b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019e4774-a67d-77c1-a5b6-57ffeeda10b5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019e4774-a67d-77c1-a5b6-57ffeeda10b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList_019e4774-a67d-7206-8e7e-e07a87df3c22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList_019e4774-a67d-7206-8e7e-e07a87df3c22" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_019e4774-a67d-7cc2-b66f-f76223046b75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_019e4774-a67d-7cc2-b66f-f76223046b75" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7360-a75e-4efe5f4c2d1e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7360-a75e-4efe5f4c2d1e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019e4774-a67d-7dfb-8610-c317aafc7495" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7360-a75e-4efe5f4c2d1e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019e4774-a67d-7dfb-8610-c317aafc7495" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019e4774-a67d-7266-b97d-c5e246be6bb9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7360-a75e-4efe5f4c2d1e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_019e4774-a67d-7266-b97d-c5e246be6bb9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_019e4774-a67d-7c45-b5d9-509d9614c3f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7360-a75e-4efe5f4c2d1e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityPurchases_019e4774-a67d-7c45-b5d9-509d9614c3f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_019e4774-a67d-7be4-b23b-666c2dc016d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_019e4774-a67d-7360-a75e-4efe5f4c2d1e" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilitySettlements_019e4774-a67d-7be4-b23b-666c2dc016d3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_019e4774-a67d-7d64-99be-4ef069b4454a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019e4774-a67d-7571-b559-13bf4b8b9307" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_019e4774-a67d-7571-b559-13bf4b8b9307" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationLiabilityGainLossStatementOfIncomeExtensibleList_019e4774-a67d-70ea-b988-d743a2f2dc67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueRecurringBasisUnobservableInputReconciliationLiabilityGainLossStatementOfIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueRecurringBasisUnobservableInputReconciliationLiabilityGainLossStatementOfIncomeExtensibleList_019e4774-a67d-70ea-b988-d743a2f2dc67" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_019e4774-a67d-7a19-825a-ab11c1c59cdd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_019e4774-a67d-79ff-a592-d0907d6ad72e" xlink:to="loc_us-gaap_FairValueLiabilityRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_019e4774-a67d-7a19-825a-ab11c1c59cdd" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesScheduleofQuantitativeInformationaboutLevel3FairValueMeasurementsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FairValueofFinancialAssetsandLiabilitiesScheduleofQuantitativeInformationaboutLevel3FairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesScheduleofQuantitativeInformationaboutLevel3FairValueMeasurementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7d45-a736-d55b4d92c1d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7472-8cf3-44557e1291ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7d45-a736-d55b4d92c1d2" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7472-8cf3-44557e1291ae" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7dcb-b74c-713a75ef35c7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7472-8cf3-44557e1291ae" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7dcb-b74c-713a75ef35c7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7dcb-b74c-713a75ef35c7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7dcb-b74c-713a75ef35c7" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7dcb-b74c-713a75ef35c7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7133-bfac-2918f83367d4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7dcb-b74c-713a75ef35c7" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7133-bfac-2918f83367d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e4774-a67d-7cf3-ad46-1150c40a9a45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7133-bfac-2918f83367d4" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e4774-a67d-7cf3-ad46-1150c40a9a45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7477-9160-d55bf5f0ce89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7472-8cf3-44557e1291ae" xlink:to="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7477-9160-d55bf5f0ce89" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7477-9160-d55bf5f0ce89_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7477-9160-d55bf5f0ce89" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7477-9160-d55bf5f0ce89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7764-ae07-2534b0bbd39b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_019e4774-a67d-7477-9160-d55bf5f0ce89" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7764-ae07-2534b0bbd39b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForwardContractsMember_019e4774-a67d-715b-bc9f-42212bfbbad8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ForwardContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7764-ae07-2534b0bbd39b" xlink:to="loc_us-gaap_ForwardContractsMember_019e4774-a67d-715b-bc9f-42212bfbbad8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a67d-7998-862f-d95776e59fe2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateLockCommitmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_019e4774-a67d-7764-ae07-2534b0bbd39b" xlink:to="loc_us-gaap_InterestRateLockCommitmentsMember_019e4774-a67d-7998-862f-d95776e59fe2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a67d-7500-98df-c77097e51611" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7472-8cf3-44557e1291ae" xlink:to="loc_srt_RangeAxis_019e4774-a67d-7500-98df-c77097e51611" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-7500-98df-c77097e51611_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7500-98df-c77097e51611" xlink:to="loc_srt_RangeMember_019e4774-a67d-7500-98df-c77097e51611_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-7d1e-a5e9-3dfd7279f1e5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7500-98df-c77097e51611" xlink:to="loc_srt_RangeMember_019e4774-a67d-7d1e-a5e9-3dfd7279f1e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a67d-7baf-a561-5cdbf17515a0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-7d1e-a5e9-3dfd7279f1e5" xlink:to="loc_srt_MinimumMember_019e4774-a67d-7baf-a561-5cdbf17515a0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a67d-71c5-95f3-f971b264bba4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-7d1e-a5e9-3dfd7279f1e5" xlink:to="loc_srt_MaximumMember_019e4774-a67d-71c5-95f3-f971b264bba4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_WeightedAverageMember_019e4774-a67d-7241-bcf8-e1a6c349e752" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_WeightedAverageMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-7d1e-a5e9-3dfd7279f1e5" xlink:to="loc_srt_WeightedAverageMember_019e4774-a67d-7241-bcf8-e1a6c349e752" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_019e4774-a67d-7b17-baf5-f7fc8e669aeb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-7472-8cf3-44557e1291ae" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_019e4774-a67d-7b17-baf5-f7fc8e669aeb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019e4774-a67d-7b17-baf5-f7fc8e669aeb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_019e4774-a67d-7b17-baf5-f7fc8e669aeb" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019e4774-a67d-7b17-baf5-f7fc8e669aeb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_019e4774-a67d-7717-a3d0-acd18f2666e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_019e4774-a67d-7b17-baf5-f7fc8e669aeb" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_019e4774-a67d-7717-a3d0-acd18f2666e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_019e4774-a67d-7b6b-919d-8d80c2e491a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019e4774-a67d-7717-a3d0-acd18f2666e6" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_019e4774-a67d-7b6b-919d-8d80c2e491a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_MeasurementInputExpectedEarnoutAndContingenciesRateMember_019e4774-a67d-7077-9d98-ca1730d3a288" xlink:href="nmrk-20260630.xsd#nmrk_MeasurementInputExpectedEarnoutAndContingenciesRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_019e4774-a67d-7717-a3d0-acd18f2666e6" xlink:to="loc_nmrk_MeasurementInputExpectedEarnoutAndContingenciesRateMember_019e4774-a67d-7077-9d98-ca1730d3a288" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_019e4774-a67d-7993-a331-48a42ba901ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7d45-a736-d55b4d92c1d2" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_019e4774-a67d-7993-a331-48a42ba901ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_019e4774-a67d-7096-9a00-79dedb8ec837" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7d45-a736-d55b4d92c1d2" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_019e4774-a67d-7096-9a00-79dedb8ec837" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_019e4774-a67d-7db0-927f-9c741d27a487" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7d45-a736-d55b4d92c1d2" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsAssetAtFairValue_019e4774-a67d-7db0-927f-9c741d27a487" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_019e4774-a67d-77bd-b804-8b64f0e384db" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7d45-a736-d55b4d92c1d2" xlink:to="loc_us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue_019e4774-a67d-77bd-b804-8b64f0e384db" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#FairValueofFinancialAssetsandLiabilitiesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/FairValueofFinancialAssetsandLiabilitiesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7c8b-9935-4a9205ec94fc" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-73d6-881f-5e97f5140f7a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7c8b-9935-4a9205ec94fc" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-73d6-881f-5e97f5140f7a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7620-a2a4-ba9c5c54a3a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-73d6-881f-5e97f5140f7a" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7620-a2a4-ba9c5c54a3a1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7620-a2a4-ba9c5c54a3a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7620-a2a4-ba9c5c54a3a1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7620-a2a4-ba9c5c54a3a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7e34-b8a7-c53fbc329bdf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_019e4774-a67d-7620-a2a4-ba9c5c54a3a1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7e34-b8a7-c53fbc329bdf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_019e4774-a67d-7dd3-9969-9f4db6b98ea0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_019e4774-a67d-7e34-b8a7-c53fbc329bdf" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_019e4774-a67d-7dd3-9969-9f4db6b98ea0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueAxis_019e4774-a67d-7bf1-b148-5670d6ff3252" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-73d6-881f-5e97f5140f7a" xlink:to="loc_us-gaap_ValuationTechniqueAxis_019e4774-a67d-7bf1-b148-5670d6ff3252" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019e4774-a67d-7bf1-b148-5670d6ff3252_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019e4774-a67d-7bf1-b148-5670d6ff3252" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019e4774-a67d-7bf1-b148-5670d6ff3252_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDomain_019e4774-a67d-7cbf-ab8f-52749e23fbf1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationTechniqueAxis_019e4774-a67d-7bf1-b148-5670d6ff3252" xlink:to="loc_us-gaap_ValuationTechniqueDomain_019e4774-a67d-7cbf-ab8f-52749e23fbf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember_019e4774-a67d-7120-9be4-aeea0e3f5065" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationTechniqueDomain_019e4774-a67d-7cbf-ab8f-52749e23fbf1" xlink:to="loc_us-gaap_ValuationTechniqueDiscountedCashFlowMember_019e4774-a67d-7120-9be4-aeea0e3f5065" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-742c-920d-fcf7cf6b3dde" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_019e4774-a67d-73d6-881f-5e97f5140f7a" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-742c-920d-fcf7cf6b3dde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-742c-920d-fcf7cf6b3dde_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-742c-920d-fcf7cf6b3dde" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-742c-920d-fcf7cf6b3dde_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7fb4-9473-08d4284223c8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_019e4774-a67d-742c-920d-fcf7cf6b3dde" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7fb4-9473-08d4284223c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019e4774-a67d-7914-a105-15762740212a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsNonrecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_019e4774-a67d-7fb4-9473-08d4284223c8" xlink:to="loc_us-gaap_FairValueMeasurementsNonrecurringMember_019e4774-a67d-7914-a105-15762740212a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_019e4774-a67d-7fd6-90d9-bde5e7961564" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7c8b-9935-4a9205ec94fc" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_019e4774-a67d-7fd6-90d9-bde5e7961564" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_BusinessCombinationContingentConsiderationLiabilityAtCost_019e4774-a67d-7e7d-9a4b-d2ac4eb804fe" xlink:href="nmrk-20260630.xsd#nmrk_BusinessCombinationContingentConsiderationLiabilityAtCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7c8b-9935-4a9205ec94fc" xlink:to="loc_nmrk_BusinessCombinationContingentConsiderationLiabilityAtCost_019e4774-a67d-7e7d-9a4b-d2ac4eb804fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AlternativeInvestment_019e4774-a67d-7002-aef6-8f7e3b75af28" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AlternativeInvestment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_019e4774-a67d-7c8b-9935-4a9205ec94fc" xlink:to="loc_us-gaap_AlternativeInvestment_019e4774-a67d-7002-aef6-8f7e3b75af28" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsServiceAgreementsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsServiceAgreementsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsServiceAgreementsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77e9-8f67-7ddc13999bd8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7d57-8a38-125ce83a9fe7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77e9-8f67-7ddc13999bd8" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7d57-8a38-125ce83a9fe7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7c29-9da3-a900069bcf24" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7d57-8a38-125ce83a9fe7" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7c29-9da3-a900069bcf24" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7c29-9da3-a900069bcf24_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7c29-9da3-a900069bcf24" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7c29-9da3-a900069bcf24_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7040-a2d7-9375fc1f365a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7c29-9da3-a900069bcf24" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7040-a2d7-9375fc1f365a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ServiceAgreementsMember_019e4774-a67d-7aa0-a4df-ca539b8d4cb0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ServiceAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7040-a2d7-9375fc1f365a" xlink:to="loc_us-gaap_ServiceAgreementsMember_019e4774-a67d-7aa0-a4df-ca539b8d4cb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7de2-b90e-a5cbd55c3e52" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7d57-8a38-125ce83a9fe7" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7de2-b90e-a5cbd55c3e52" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7de2-b90e-a5cbd55c3e52_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7de2-b90e-a5cbd55c3e52" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7de2-b90e-a5cbd55c3e52_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7a0e-9038-3bd8bd0a115c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7de2-b90e-a5cbd55c3e52" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7a0e-9038-3bd8bd0a115c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-74c3-a10c-6040718a2854" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7a0e-9038-3bd8bd0a115c" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-74c3-a10c-6040718a2854" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfessionalFees_019e4774-a67d-7e47-b19d-be95b8e1b019" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProfessionalFees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77e9-8f67-7ddc13999bd8" xlink:to="loc_us-gaap_ProfessionalFees_019e4774-a67d-7e47-b19d-be95b8e1b019" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsLoansForgivableLoansandOtherReceivablesfromEmployeesandPartnersDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsLoansForgivableLoansandOtherReceivablesfromEmployeesandPartnersDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsLoansForgivableLoansandOtherReceivablesfromEmployeesandPartnersDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7086-a4ae-dc19a7c9cd9f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-75ed-bd50-e21df47054f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7086-a4ae-dc19a7c9cd9f" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-75ed-bd50-e21df47054f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7251-96bc-2a4618639004" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-75ed-bd50-e21df47054f2" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7251-96bc-2a4618639004" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7251-96bc-2a4618639004_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7251-96bc-2a4618639004" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7251-96bc-2a4618639004_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-791d-9dc9-07178cf77405" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7251-96bc-2a4618639004" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-791d-9dc9-07178cf77405" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-733e-b3f4-4719843790e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-791d-9dc9-07178cf77405" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-733e-b3f4-4719843790e8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-787e-9e42-104c7afe736a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-75ed-bd50-e21df47054f2" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-787e-9e42-104c7afe736a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-787e-9e42-104c7afe736a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-787e-9e42-104c7afe736a" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-787e-9e42-104c7afe736a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7fb3-81cd-2993502f6fd3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-787e-9e42-104c7afe736a" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7fb3-81cd-2993502f6fd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_EmployeeLoansCompensationExpenseMember_019e4774-a67d-762b-87a2-6b2bbf02b5b0" xlink:href="nmrk-20260630.xsd#nmrk_EmployeeLoansCompensationExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7fb3-81cd-2993502f6fd3" xlink:to="loc_nmrk_EmployeeLoansCompensationExpenseMember_019e4774-a67d-762b-87a2-6b2bbf02b5b0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent_019e4774-a67d-712f-890c-d0f1b038ce0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7086-a4ae-dc19a7c9cd9f" xlink:to="loc_us-gaap_OtherReceivableAfterAllowanceForCreditLossNoncurrent_019e4774-a67d-712f-890c-d0f1b038ce0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LaborAndRelatedExpense_019e4774-a67d-7d92-a5ac-31aa08f2796a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LaborAndRelatedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7086-a4ae-dc19a7c9cd9f" xlink:to="loc_us-gaap_LaborAndRelatedExpense_019e4774-a67d-7d92-a5ac-31aa08f2796a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithCantorCommercialRealEstateLPDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithCantorCommercialRealEstateLPDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithCantorCommercialRealEstateLPDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7520-9fc6-31fd8dbd4b75" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-785d-8896-1a95c65f392e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7520-9fc6-31fd8dbd4b75" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-785d-8896-1a95c65f392e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-79da-a1d2-f78cb50603a9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-785d-8896-1a95c65f392e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-79da-a1d2-f78cb50603a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-79da-a1d2-f78cb50603a9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-79da-a1d2-f78cb50603a9" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-79da-a1d2-f78cb50603a9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7ebb-8a48-940e449c7e27" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-79da-a1d2-f78cb50603a9" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7ebb-8a48-940e449c7e27" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-7e12-9738-47911bbe0bc2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7ebb-8a48-940e449c7e27" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-7e12-9738-47911bbe0bc2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FeesAndCommissionsMortgageBankingAndServicing_019e4774-a67d-780d-9fb5-0d55af87e28a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FeesAndCommissionsMortgageBankingAndServicing"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7520-9fc6-31fd8dbd4b75" xlink:to="loc_us-gaap_FeesAndCommissionsMortgageBankingAndServicing_019e4774-a67d-780d-9fb5-0d55af87e28a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsHowardBrandonLutnickDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsHowardBrandonLutnickDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsHowardBrandonLutnickDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019fd008-d640-78fa-87f4-f45ae22efb76" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fd008-d640-7404-8275-0123e96079e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fd008-d640-78fa-87f4-f45ae22efb76" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fd008-d640-7404-8275-0123e96079e1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019fd00a-31b8-76de-9cfe-2d00f4860152" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fd008-d640-7404-8275-0123e96079e1" xlink:to="loc_srt_CounterpartyNameAxis_019fd00a-31b8-76de-9cfe-2d00f4860152" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-76de-9cfe-2d00f4860152_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019fd00a-31b8-76de-9cfe-2d00f4860152" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-76de-9cfe-2d00f4860152_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-77fc-a6c5-21d4262cfeaf" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019fd00a-31b8-76de-9cfe-2d00f4860152" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-77fc-a6c5-21d4262cfeaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CFGroupManagementInc.Member_019fd00a-31b8-7886-a322-d64faa48cb2e" xlink:href="nmrk-20260630.xsd#nmrk_CFGroupManagementInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-77fc-a6c5-21d4262cfeaf" xlink:to="loc_nmrk_CFGroupManagementInc.Member_019fd00a-31b8-7886-a322-d64faa48cb2e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_HowardW.LutnickSpouseAndTrustsMember_019fd00a-31b8-7108-b25d-21c24d5fdf41" xlink:href="nmrk-20260630.xsd#nmrk_HowardW.LutnickSpouseAndTrustsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-77fc-a6c5-21d4262cfeaf" xlink:to="loc_nmrk_HowardW.LutnickSpouseAndTrustsMember_019fd00a-31b8-7108-b25d-21c24d5fdf41" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_HowardW.LutnickSpouseMember_019fd00a-31b8-7b98-90fb-bdd97f665cdb" xlink:href="nmrk-20260630.xsd#nmrk_HowardW.LutnickSpouseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019fd00a-31b8-77fc-a6c5-21d4262cfeaf" xlink:to="loc_nmrk_HowardW.LutnickSpouseMember_019fd00a-31b8-7b98-90fb-bdd97f665cdb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019fd00a-31b8-7450-9174-cac1e01b5634" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fd008-d640-7404-8275-0123e96079e1" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019fd00a-31b8-7450-9174-cac1e01b5634" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019fd00a-31b8-7450-9174-cac1e01b5634_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019fd00a-31b8-7450-9174-cac1e01b5634" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019fd00a-31b8-7450-9174-cac1e01b5634_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019fd00a-31b8-74cf-a2fc-2e72d8e915d6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019fd00a-31b8-7450-9174-cac1e01b5634" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019fd00a-31b8-74cf-a2fc-2e72d8e915d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_SaleOfClassACommonStockToCompanyMember_019fd00a-31b8-7751-a763-512238a4190f" xlink:href="nmrk-20260630.xsd#nmrk_SaleOfClassACommonStockToCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019fd00a-31b8-74cf-a2fc-2e72d8e915d6" xlink:to="loc_nmrk_SaleOfClassACommonStockToCompanyMember_019fd00a-31b8-7751-a763-512238a4190f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fd00a-31b8-70d6-9fee-d0c5e388445f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019fd008-d640-7404-8275-0123e96079e1" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fd00a-31b8-70d6-9fee-d0c5e388445f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fd00a-31b8-70d6-9fee-d0c5e388445f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fd00a-31b8-70d6-9fee-d0c5e388445f" xlink:to="loc_us-gaap_RelatedPartyDomain_019fd00a-31b8-70d6-9fee-d0c5e388445f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fd00a-31b8-7c08-981c-cf93af17b747" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fd00a-31b8-70d6-9fee-d0c5e388445f" xlink:to="loc_us-gaap_RelatedPartyDomain_019fd00a-31b8-7c08-981c-cf93af17b747" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_BoardOfDirectorsChairmanMember_019fd00a-31b8-7f67-8269-779ae8ae814c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_BoardOfDirectorsChairmanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fd00a-31b8-7c08-981c-cf93af17b747" xlink:to="loc_srt_BoardOfDirectorsChairmanMember_019fd00a-31b8-7f67-8269-779ae8ae814c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019fd00a-31b8-7d29-a655-e6ea29c6faf3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fd008-d640-78fa-87f4-f45ae22efb76" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_019fd00a-31b8-7d29-a655-e6ea29c6faf3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019fd00a-31b8-735b-b912-6beeb6717087" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019fd008-d640-78fa-87f4-f45ae22efb76" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019fd00a-31b8-735b-b912-6beeb6717087" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsBarryGosinDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsBarryGosinDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsBarryGosinDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7906-9a68-06c64b557fac" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7906-9a68-06c64b557fac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710d-e8bb-7953-82a3-db5070c82a58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7906-9a68-06c64b557fac" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710d-e8bb-7953-82a3-db5070c82a58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f710d-e8bb-7953-82a3-db5070c82a58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710d-e8bb-7953-82a3-db5070c82a58" xlink:to="loc_us-gaap_RelatedPartyDomain_019f710d-e8bb-7953-82a3-db5070c82a58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f710d-e8bb-7fc9-bb71-7bcf84d0069a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710d-e8bb-7953-82a3-db5070c82a58" xlink:to="loc_us-gaap_RelatedPartyDomain_019f710d-e8bb-7fc9-bb71-7bcf84d0069a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefExecutiveOfficerMember_019f710d-e8bb-7dfd-b213-0ab4d8e97424" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ChiefExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019f710d-e8bb-7fc9-bb71-7bcf84d0069a" xlink:to="loc_srt_ChiefExecutiveOfficerMember_019f710d-e8bb-7dfd-b213-0ab4d8e97424" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710d-e8bb-756e-aa61-7a5446464765" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7906-9a68-06c64b557fac" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710d-e8bb-756e-aa61-7a5446464765" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710d-e8bb-756e-aa61-7a5446464765_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710d-e8bb-756e-aa61-7a5446464765" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710d-e8bb-756e-aa61-7a5446464765_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710d-e8bb-7cd5-a982-44d53b5c6699" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710d-e8bb-756e-aa61-7a5446464765" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710d-e8bb-7cd5-a982-44d53b5c6699" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NewmarkHoldingsNPSUsMember_019f710d-e8bb-7dcf-9c70-8416aa51ef2a" xlink:href="nmrk-20260630.xsd#nmrk_NewmarkHoldingsNPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710d-e8bb-7cd5-a982-44d53b5c6699" xlink:to="loc_nmrk_NewmarkHoldingsNPSUsMember_019f710d-e8bb-7dcf-9c70-8416aa51ef2a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateAxis_019f710d-e8bb-7f44-a4cd-8c3de1f2ab03" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7906-9a68-06c64b557fac" xlink:to="loc_us-gaap_AwardDateAxis_019f710d-e8bb-7f44-a4cd-8c3de1f2ab03" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7f44-a4cd-8c3de1f2ab03_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardDateAxis_019f710d-e8bb-7f44-a4cd-8c3de1f2ab03" xlink:to="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7f44-a4cd-8c3de1f2ab03_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7445-83d5-b6f245ba6db9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardDateDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardDateAxis_019f710d-e8bb-7f44-a4cd-8c3de1f2ab03" xlink:to="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7445-83d5-b6f245ba6db9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_AwardPeriodOneMember_019f710d-e8bb-7d4c-af3d-564adedb7581" xlink:href="nmrk-20260630.xsd#nmrk_AwardPeriodOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7445-83d5-b6f245ba6db9" xlink:to="loc_nmrk_AwardPeriodOneMember_019f710d-e8bb-7d4c-af3d-564adedb7581" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_AwardPeriodTwoMember_019f710d-e8bb-7fad-9a25-8d3a090040a7" xlink:href="nmrk-20260630.xsd#nmrk_AwardPeriodTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7445-83d5-b6f245ba6db9" xlink:to="loc_nmrk_AwardPeriodTwoMember_019f710d-e8bb-7fad-9a25-8d3a090040a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_AwardPeriodThreeMember_019f710d-e8bb-7f49-9b25-6681b9f5deef" xlink:href="nmrk-20260630.xsd#nmrk_AwardPeriodThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AwardDateDomain_019f710d-e8bb-7445-83d5-b6f245ba6db9" xlink:to="loc_nmrk_AwardPeriodThreeMember_019f710d-e8bb-7f49-9b25-6681b9f5deef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionTerminationNoticePeriod_019f710d-e8bb-7909-ba55-89ab17def618" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionTerminationNoticePeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionTerminationNoticePeriod_019f710d-e8bb-7909-ba55-89ab17def618" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionOneTimeCashPayment_019f710d-e8bb-7707-8c91-7d90bc02416a" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionOneTimeCashPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionOneTimeCashPayment_019f710d-e8bb-7707-8c91-7d90bc02416a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019f710d-e8bb-7cf1-bcdd-bf258d244a8b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019f710d-e8bb-7cf1-bcdd-bf258d244a8b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid_019f710d-e8bb-7a22-8026-dbf1aafc3b3c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareBasedLiabilitiesPaid_019f710d-e8bb-7a22-8026-dbf1aafc3b3c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAnnualCompensation_019f710d-e8bb-740f-a3a6-36960b2c76ed" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAnnualCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionAnnualCompensation_019f710d-e8bb-740f-a3a6-36960b2c76ed" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAnnualCompensationSalary_019f710d-e8bb-784d-88d0-95f4d460b611" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAnnualCompensationSalary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionAnnualCompensationSalary_019f710d-e8bb-784d-88d0-95f4d460b611" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAnnualCompensationCashBasedAndShareBasedAwards_019f710d-e8bb-7a17-aa41-08be6cf2833d" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAnnualCompensationCashBasedAndShareBasedAwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionAnnualCompensationCashBasedAndShareBasedAwards_019f710d-e8bb-7a17-aa41-08be6cf2833d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightConversionPercentage_019f710d-e8bb-721a-8697-44b76740444f" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightConversionPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightConversionPercentage_019f710d-e8bb-721a-8697-44b76740444f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightPercentage_019f710d-e8bb-71d9-b4d8-be931d6dadfb" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightPercentage_019f710d-e8bb-71d9-b4d8-be931d6dadfb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightThresholdMinimumGrossRevenue_019f710d-e8bb-7cfb-9c19-05baa54ab127" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightThresholdMinimumGrossRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightThresholdMinimumGrossRevenue_019f710d-e8bb-7cfb-9c19-05baa54ab127" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightRightsExchanged_019f710d-e8bb-7902-b640-3f54b4804127" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightRightsExchanged"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightRightsExchanged_019f710d-e8bb-7902-b640-3f54b4804127" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAnnualCashBonus_019f710d-e8bb-7b33-804e-01a949faf562" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAnnualCashBonus"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionAnnualCashBonus_019f710d-e8bb-7b33-804e-01a949faf562" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightNumberOfTranches_019f710d-e8bb-7d69-818f-4277e3a098f5" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightNumberOfTranches"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightNumberOfTranches_019f710d-e8bb-7d69-818f-4277e3a098f5" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightAdvanceAward_019f710d-e8bb-7322-a85e-dee1458061c0" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightAdvanceAward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightAdvanceAward_019f710d-e8bb-7322-a85e-dee1458061c0" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionUpfrontAdvanceAwardBaseForCalculatingNumberOfRightsInPeriod_019f710d-e8bb-7d8d-bf9f-71cbf48fc5ae" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionUpfrontAdvanceAwardBaseForCalculatingNumberOfRightsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_RelatedPartyTransactionUpfrontAdvanceAwardBaseForCalculatingNumberOfRightsInPeriod_019f710d-e8bb-7d8d-bf9f-71cbf48fc5ae" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019f710d-e8bb-7a2f-a21b-7afd9b5930bd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_us-gaap_SharePrice_019f710d-e8bb-7a2f-a21b-7afd9b5930bd" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightTrancheOne_019f710e-5661-7daf-94a4-06de1603b078" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightTrancheOne"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightTrancheOne_019f710e-5661-7daf-94a4-06de1603b078" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightNumberOfInstallments_019f710e-5661-7b69-aa66-8a6bf65c47f8" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightNumberOfInstallments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightNumberOfInstallments_019f710e-5661-7b69-aa66-8a6bf65c47f8" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightTrancheTwo_019f710e-5661-7cc5-9c00-60565b6a6dfc" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightTrancheTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightTrancheTwo_019f710e-5661-7cc5-9c00-60565b6a6dfc" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightTrancheThree_019f710e-5661-781f-8591-336fe9aa3bf1" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightTrancheThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightTrancheThree_019f710e-5661-781f-8591-336fe9aa3bf1" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightTrancheFour_019f710e-5661-7d30-bb50-b90957aa2bb6" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightTrancheFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-77db-a128-2abc01c15473" xlink:to="loc_nmrk_ClassOfWarrantOrRightTrancheFour_019f710e-5661-7d30-bb50-b90957aa2bb6" xlink:type="arc" order="20"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsMichaelRispoliDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsMichaelRispoliDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsMichaelRispoliDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f67-9423-dc02c4398bcd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f67-9423-dc02c4398bcd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019f710e-e587-77f0-876c-08475c7ec452" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f67-9423-dc02c4398bcd" xlink:to="loc_us-gaap_AwardTypeAxis_019f710e-e587-77f0-876c-08475c7ec452" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f710e-e587-77f0-876c-08475c7ec452_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019f710e-e587-77f0-876c-08475c7ec452" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f710e-e587-77f0-876c-08475c7ec452_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f710e-e587-7c01-b4e1-3374edb9c2a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019f710e-e587-77f0-876c-08475c7ec452" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f710e-e587-7c01-b4e1-3374edb9c2a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019f710e-e587-77e5-8169-05628155d04c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f710e-e587-7c01-b4e1-3374edb9c2a8" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019f710e-e587-77e5-8169-05628155d04c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710e-e587-7ad6-a1e5-278fb6a5bb58" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f67-9423-dc02c4398bcd" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710e-e587-7ad6-a1e5-278fb6a5bb58" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f710e-e587-7ad6-a1e5-278fb6a5bb58_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710e-e587-7ad6-a1e5-278fb6a5bb58" xlink:to="loc_us-gaap_RelatedPartyDomain_019f710e-e587-7ad6-a1e5-278fb6a5bb58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f710e-e587-79a7-9b27-fcbf46e7f404" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f710e-e587-7ad6-a1e5-278fb6a5bb58" xlink:to="loc_us-gaap_RelatedPartyDomain_019f710e-e587-79a7-9b27-fcbf46e7f404" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefFinancialOfficerMember_019f710e-e587-7520-b471-6c32760a000b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ChiefFinancialOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019f710e-e587-79a7-9b27-fcbf46e7f404" xlink:to="loc_srt_ChiefFinancialOfficerMember_019f710e-e587-7520-b471-6c32760a000b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710e-e587-786a-8c45-45beae3596ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f67-9423-dc02c4398bcd" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710e-e587-786a-8c45-45beae3596ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-786a-8c45-45beae3596ef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710e-e587-786a-8c45-45beae3596ef" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-786a-8c45-45beae3596ef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-7652-b9ca-1e3028567c78" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019f710e-e587-786a-8c45-45beae3596ef" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-7652-b9ca-1e3028567c78" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NewmarkHoldingsPSUMember_019f710e-e587-72a3-8838-ecdd63a76d7b" xlink:href="nmrk-20260630.xsd#nmrk_NewmarkHoldingsPSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-7652-b9ca-1e3028567c78" xlink:to="loc_nmrk_NewmarkHoldingsPSUMember_019f710e-e587-72a3-8838-ecdd63a76d7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NewmarkHoldingsPPSUMember_019f710e-e587-77bc-94fe-1ffb8218a020" xlink:href="nmrk-20260630.xsd#nmrk_NewmarkHoldingsPPSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-7652-b9ca-1e3028567c78" xlink:to="loc_nmrk_NewmarkHoldingsPPSUMember_019f710e-e587-77bc-94fe-1ffb8218a020" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NonExchangeableNewmarkHoldingsPSUsMember_019f710e-e587-7f61-a43b-e1dc7c77869b" xlink:href="nmrk-20260630.xsd#nmrk_NonExchangeableNewmarkHoldingsPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-7652-b9ca-1e3028567c78" xlink:to="loc_nmrk_NonExchangeableNewmarkHoldingsPSUsMember_019f710e-e587-7f61-a43b-e1dc7c77869b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NonExchangeableRightsForNewmarkHoldingsPPSUsMember_019f710e-e587-7769-8b69-2d4d27b45501" xlink:href="nmrk-20260630.xsd#nmrk_NonExchangeableRightsForNewmarkHoldingsPPSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019f710e-e587-7652-b9ca-1e3028567c78" xlink:to="loc_nmrk_NonExchangeableRightsForNewmarkHoldingsPPSUsMember_019f710e-e587-7769-8b69-2d4d27b45501" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingAxis_019f710e-e587-7280-a6ff-ec12a8276bc8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f67-9423-dc02c4398bcd" xlink:to="loc_us-gaap_VestingAxis_019f710e-e587-7280-a6ff-ec12a8276bc8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_019f710e-e587-7280-a6ff-ec12a8276bc8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VestingAxis_019f710e-e587-7280-a6ff-ec12a8276bc8" xlink:to="loc_us-gaap_VestingDomain_019f710e-e587-7280-a6ff-ec12a8276bc8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_VestingDomain_019f710e-e587-7fe3-941a-974626d9dffb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VestingAxis_019f710e-e587-7280-a6ff-ec12a8276bc8" xlink:to="loc_us-gaap_VestingDomain_019f710e-e587-7fe3-941a-974626d9dffb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_019f710e-e587-7961-80a8-de9aeb489388" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheOneMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019f710e-e587-7fe3-941a-974626d9dffb" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheOneMember_019f710e-e587-7961-80a8-de9aeb489388" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_019f710e-e587-7fb8-9a01-4b1baf07f112" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019f710e-e587-7fe3-941a-974626d9dffb" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheTwoMember_019f710e-e587-7fb8-9a01-4b1baf07f112" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_019f710e-e587-7045-a064-5367e41f3229" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationAwardTrancheThreeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VestingDomain_019f710e-e587-7fe3-941a-974626d9dffb" xlink:to="loc_us-gaap_ShareBasedCompensationAwardTrancheThreeMember_019f710e-e587-7045-a064-5367e41f3229" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019f93ac-8ebf-756c-a2e2-fbbd62977471" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019f93ac-8ebf-756c-a2e2-fbbd62977471" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019f93af-c6d0-753a-b10e-5a864d67aa87" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019f93af-c6d0-753a-b10e-5a864d67aa87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019f710e-e587-7ace-b4cf-2ff54814be67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_SharePrice_019f710e-e587-7ace-b4cf-2ff54814be67" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019f93b1-2498-779c-a49e-e7cfe0c643f8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019f93b1-2498-779c-a49e-e7cfe0c643f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightRightsReceivingExchangeability_019f710e-e587-7a5c-94aa-7a1a003bc47f" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightRightsReceivingExchangeability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_nmrk_ClassOfWarrantOrRightRightsReceivingExchangeability_019f710e-e587-7a5c-94aa-7a1a003bc47f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightCashWaived_019f710e-e587-7bd7-a878-c99a3dd3b9e0" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightCashWaived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_nmrk_ClassOfWarrantOrRightCashWaived_019f710e-e587-7bd7-a878-c99a3dd3b9e0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019f710e-e587-77e5-bf9d-755c83501ef2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_019f710e-e587-77e5-bf9d-755c83501ef2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019f710e-e587-7b83-9b6b-b27253571d47" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019f710e-e587-7b83-9b6b-b27253571d47" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightPercentageReceivingExchangeability_019f710e-e587-7d6d-b48d-26f4f691ddbf" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightPercentageReceivingExchangeability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_nmrk_ClassOfWarrantOrRightPercentageReceivingExchangeability_019f710e-e587-7d6d-b48d-26f4f691ddbf" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantsOrRightExchangeable_019f710e-e587-771f-ac6b-37885ad5d749" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantsOrRightExchangeable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_nmrk_ClassOfWarrantsOrRightExchangeable_019f710e-e587-771f-ac6b-37885ad5d749" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantsAndRightsOutstanding_019f710e-e587-73f1-8c37-4fb33aab8f66" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantsAndRightsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_us-gaap_WarrantsAndRightsOutstanding_019f710e-e587-73f1-8c37-4fb33aab8f66" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightPercentageReceivingExchangeabilityProRata_019f8186-ad0b-7b87-ad46-e427734d27a7" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightPercentageReceivingExchangeabilityProRata"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7089-a7b5-5a11e84e9b46" xlink:to="loc_nmrk_ClassOfWarrantOrRightPercentageReceivingExchangeabilityProRata_019f8186-ad0b-7b87-ad46-e427734d27a7" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsStephenMerkelDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsStephenMerkelDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsStephenMerkelDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-707f-93b9-5d83ffa0de29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-707f-93b9-5d83ffa0de29" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93b9-923d-7714-8b6e-e2fa66ed1700" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-707f-93b9-5d83ffa0de29" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93b9-923d-7714-8b6e-e2fa66ed1700" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f93b9-923d-7714-8b6e-e2fa66ed1700_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93b9-923d-7714-8b6e-e2fa66ed1700" xlink:to="loc_us-gaap_RelatedPartyDomain_019f93b9-923d-7714-8b6e-e2fa66ed1700_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f93b9-923d-7751-bbdd-32f8dcb73f61" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93b9-923d-7714-8b6e-e2fa66ed1700" xlink:to="loc_us-gaap_RelatedPartyDomain_019f93b9-923d-7751-bbdd-32f8dcb73f61" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ExecutiveVicePresidentMember_019f93b9-923d-7ab6-8154-5374e0e41703" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ExecutiveVicePresidentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019f93b9-923d-7751-bbdd-32f8dcb73f61" xlink:to="loc_srt_ExecutiveVicePresidentMember_019f93b9-923d-7ab6-8154-5374e0e41703" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019f93b9-923d-7685-b84a-4cdbb1f1c92b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-707f-93b9-5d83ffa0de29" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019f93b9-923d-7685-b84a-4cdbb1f1c92b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019f93b9-923d-7685-b84a-4cdbb1f1c92b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019f93b9-923d-7685-b84a-4cdbb1f1c92b" xlink:to="loc_us-gaap_ClassOfStockDomain_019f93b9-923d-7685-b84a-4cdbb1f1c92b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019f93b9-923d-73ff-8be5-010a96f1553f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019f93b9-923d-7685-b84a-4cdbb1f1c92b" xlink:to="loc_us-gaap_ClassOfStockDomain_019f93b9-923d-73ff-8be5-010a96f1553f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019f93b9-923d-771d-aea4-25bca4a41053" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019f93b9-923d-73ff-8be5-010a96f1553f" xlink:to="loc_us-gaap_CommonClassAMember_019f93b9-923d-771d-aea4-25bca4a41053" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_019f93b9-923d-7826-a9be-04797eeed283" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-707f-93b9-5d83ffa0de29" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_019f93b9-923d-7826-a9be-04797eeed283" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019f93b9-923d-7826-a9be-04797eeed283_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019f93b9-923d-7826-a9be-04797eeed283" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019f93b9-923d-7826-a9be-04797eeed283_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_019f93b9-923d-7063-b1e5-1a28468b324a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_019f93b9-923d-7826-a9be-04797eeed283" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_019f93b9-923d-7063-b1e5-1a28468b324a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NonExchangeableMr.MerkelHoldingsMember_019f93b9-923d-780f-bbd8-9a958f48c04c" xlink:href="nmrk-20260630.xsd#nmrk_NonExchangeableMr.MerkelHoldingsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_019f93b9-923d-7063-b1e5-1a28468b324a" xlink:to="loc_nmrk_NonExchangeableMr.MerkelHoldingsMember_019f93b9-923d-780f-bbd8-9a958f48c04c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_019f93b9-923d-74cd-b74a-2b99ce256eb6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_019f93b9-923d-74cd-b74a-2b99ce256eb6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_StockRedeemedOrCalledDuringPeriodSharesGross_019f93b9-923d-7a86-bd86-f831674e7700" xlink:href="nmrk-20260630.xsd#nmrk_StockRedeemedOrCalledDuringPeriodSharesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_StockRedeemedOrCalledDuringPeriodSharesGross_019f93b9-923d-7a86-bd86-f831674e7700" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_019f93b9-923d-7e7a-8c35-583c6be66bf0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_019f93b9-923d-7e7a-8c35-583c6be66bf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightConversionRatio_019f93b9-923d-7895-9309-54d84900c70d" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightConversionRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_ClassOfWarrantOrRightConversionRatio_019f93b9-923d-7895-9309-54d84900c70d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_StockRedeemedOrCalledDuringPeriodSharesWithheldForTaxWithholdingObligationShares_019f93b9-923d-7c5e-8766-280b13e89504" xlink:href="nmrk-20260630.xsd#nmrk_StockRedeemedOrCalledDuringPeriodSharesWithheldForTaxWithholdingObligationShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_StockRedeemedOrCalledDuringPeriodSharesWithheldForTaxWithholdingObligationShares_019f93b9-923d-7c5e-8766-280b13e89504" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019f93b9-923d-7a8d-925d-57c3bce31089" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_us-gaap_SharePrice_019f93b9-923d-7a8d-925d-57c3bce31089" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_019f93b9-923d-7fe9-a187-ff35da6c3680" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRedeemedOrCalledDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_us-gaap_StockRedeemedOrCalledDuringPeriodShares_019f93b9-923d-7fe9-a187-ff35da6c3680" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ClassOfWarrantOrRightCashWaived_019f93b9-923d-7837-80a6-e200ee7a61af" xlink:href="nmrk-20260630.xsd#nmrk_ClassOfWarrantOrRightCashWaived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_ClassOfWarrantOrRightCashWaived_019f93b9-923d-7837-80a6-e200ee7a61af" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RestructuringAndRelatedCostShareBasedPaymentArrangementVestingPeriod_019f93b9-923d-7ca2-ab4f-5a90dc2b3927" xlink:href="nmrk-20260630.xsd#nmrk_RestructuringAndRelatedCostShareBasedPaymentArrangementVestingPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_RestructuringAndRelatedCostShareBasedPaymentArrangementVestingPeriod_019f93b9-923d-7ca2-ab4f-5a90dc2b3927" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RestructuringAndRelatedCostSeveranceCostsLumpSumPaymentTerminationPeriod_019f93b9-923d-7d18-8187-d57a87421cd5" xlink:href="nmrk-20260630.xsd#nmrk_RestructuringAndRelatedCostSeveranceCostsLumpSumPaymentTerminationPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_RestructuringAndRelatedCostSeveranceCostsLumpSumPaymentTerminationPeriod_019f93b9-923d-7d18-8187-d57a87421cd5" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RestructuringAndRelatedCostSeveranceCostsMedicalBenefitsPeriod_019f93b9-923d-7188-a3c6-c0b0f69a68a0" xlink:href="nmrk-20260630.xsd#nmrk_RestructuringAndRelatedCostSeveranceCostsMedicalBenefitsPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e9b-9fa3-6c00a39ce2a7" xlink:to="loc_nmrk_RestructuringAndRelatedCostSeveranceCostsMedicalBenefitsPeriod_019f93b9-923d-7188-a3c6-c0b0f69a68a0" xlink:type="arc" order="10"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsKyleLutnickDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsKyleLutnickDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsKyleLutnickDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DefinedBenefitPlanDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e4774-a67d-7ee0-8683-602b51c7bf6e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:to="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e4774-a67d-7ee0-8683-602b51c7bf6e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019f93bb-6cbf-7fcb-83e6-9bad607f1124" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e4774-a67d-7ee0-8683-602b51c7bf6e" xlink:to="loc_us-gaap_AwardTypeAxis_019f93bb-6cbf-7fcb-83e6-9bad607f1124" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bb-6cbf-7fcb-83e6-9bad607f1124_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019f93bb-6cbf-7fcb-83e6-9bad607f1124" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bb-6cbf-7fcb-83e6-9bad607f1124_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bb-6cbf-74de-b146-be5fd2454e4b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019f93bb-6cbf-7fcb-83e6-9bad607f1124" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bb-6cbf-74de-b146-be5fd2454e4b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019f93bb-6cbf-7a3f-8cfd-debadb70ab6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bb-6cbf-74de-b146-be5fd2454e4b" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019f93bb-6cbf-7a3f-8cfd-debadb70ab6b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bb-6cbf-70ba-955b-fc2843237bab" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfDefinedBenefitPlansDisclosuresTable_019e4774-a67d-7ee0-8683-602b51c7bf6e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bb-6cbf-70ba-955b-fc2843237bab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f93bb-6cbf-70ba-955b-fc2843237bab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bb-6cbf-70ba-955b-fc2843237bab" xlink:to="loc_us-gaap_RelatedPartyDomain_019f93bb-6cbf-70ba-955b-fc2843237bab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f93bb-6cbf-7b94-b1f8-cd10a7266b49" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bb-6cbf-70ba-955b-fc2843237bab" xlink:to="loc_us-gaap_RelatedPartyDomain_019f93bb-6cbf-7b94-b1f8-cd10a7266b49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_DirectorMember_019f93bb-6cbf-7a79-bfae-1d469963987e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_DirectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019f93bb-6cbf-7b94-b1f8-cd10a7266b49" xlink:to="loc_srt_DirectorMember_019f93bb-6cbf-7a79-bfae-1d469963987e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019f93bb-6cbf-7a5b-a3d6-625237d859f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019f93bb-6cbf-7a5b-a3d6-625237d859f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019f93bb-6cbf-7603-805c-f3c279372307" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019f93bb-6cbf-7603-805c-f3c279372307" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019f93bb-6cbf-7c9d-9e74-42530da66515" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:to="loc_us-gaap_SharePrice_019f93bb-6cbf-7c9d-9e74-42530da66515" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019f93bb-6cbf-7573-9ab5-e37926811638" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019f93bb-6cbf-7573-9ab5-e37926811638" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionEmployeeCompensationAnnualCompensation_019f93bb-6cbf-7788-a634-b64a1a62d897" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionEmployeeCompensationAnnualCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DefinedBenefitPlanDisclosureLineItems_019e4774-a67d-727d-b6f1-7b0f77af19ff" xlink:to="loc_nmrk_RelatedPartyTransactionEmployeeCompensationAnnualCompensation_019f93bb-6cbf-7788-a634-b64a1a62d897" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsLuisAlvaradoDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsLuisAlvaradoDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsTransactionswithExecutiveOfficersandDirectorsLuisAlvaradoDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7755-ad55-9633bbe9e43e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7755-ad55-9633bbe9e43e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019f93bd-0723-76b5-81bf-416ec13ba9dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7755-ad55-9633bbe9e43e" xlink:to="loc_us-gaap_AwardTypeAxis_019f93bd-0723-76b5-81bf-416ec13ba9dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bd-0723-76b5-81bf-416ec13ba9dd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019f93bd-0723-76b5-81bf-416ec13ba9dd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bd-0723-76b5-81bf-416ec13ba9dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bd-0723-74c2-8b0e-97b3306b7b48" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019f93bd-0723-76b5-81bf-416ec13ba9dd" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bd-0723-74c2-8b0e-97b3306b7b48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019f93bd-0723-7532-a55e-65f6081da1d3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019f93bd-0723-74c2-8b0e-97b3306b7b48" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019f93bd-0723-7532-a55e-65f6081da1d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bd-0723-7d14-926b-6b98f5ef4cc0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7755-ad55-9633bbe9e43e" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bd-0723-7d14-926b-6b98f5ef4cc0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f93bd-0723-7d14-926b-6b98f5ef4cc0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bd-0723-7d14-926b-6b98f5ef4cc0" xlink:to="loc_us-gaap_RelatedPartyDomain_019f93bd-0723-7d14-926b-6b98f5ef4cc0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019f93bd-0723-71a9-b1bc-8417a16cc094" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019f93bd-0723-7d14-926b-6b98f5ef4cc0" xlink:to="loc_us-gaap_RelatedPartyDomain_019f93bd-0723-71a9-b1bc-8417a16cc094" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefOperatingOfficerMember_019f93bd-0723-7887-b92f-1ba70280d252" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ChiefOperatingOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019f93bd-0723-71a9-b1bc-8417a16cc094" xlink:to="loc_srt_ChiefOperatingOfficerMember_019f93bd-0723-7887-b92f-1ba70280d252" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019f93bd-0723-7491-ad98-58b0bfca7e98" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019f93bd-0723-71a9-b1bc-8417a16cc094" xlink:to="loc_us-gaap_RelatedPartyMember_019f93bd-0723-7491-ad98-58b0bfca7e98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019f93bd-0723-74b8-b0a0-7149d0ae5a26" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7755-ad55-9633bbe9e43e" xlink:to="loc_srt_CounterpartyNameAxis_019f93bd-0723-74b8-b0a0-7149d0ae5a26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f93bd-0723-74b8-b0a0-7149d0ae5a26_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019f93bd-0723-74b8-b0a0-7149d0ae5a26" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f93bd-0723-74b8-b0a0-7149d0ae5a26_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f93bd-0723-76ff-8e5b-c44b3e1208f9" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019f93bd-0723-74b8-b0a0-7149d0ae5a26" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f93bd-0723-76ff-8e5b-c44b3e1208f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_Mr.JosephAlvaradoMember_019f93bd-0723-7b21-9cda-e9af84cf8597" xlink:href="nmrk-20260630.xsd#nmrk_Mr.JosephAlvaradoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f93bd-0723-76ff-8e5b-c44b3e1208f9" xlink:to="loc_nmrk_Mr.JosephAlvaradoMember_019f93bd-0723-7b21-9cda-e9af84cf8597" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_Mr.RobertAlvaradoMember_019f93bd-0723-7c01-b63b-390172ee5a00" xlink:href="nmrk-20260630.xsd#nmrk_Mr.RobertAlvaradoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019f93bd-0723-76ff-8e5b-c44b3e1208f9" xlink:to="loc_nmrk_Mr.RobertAlvaradoMember_019f93bd-0723-7c01-b63b-390172ee5a00" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019f93bd-0723-7e30-899e-4e2fc854f56e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7755-ad55-9633bbe9e43e" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019f93bd-0723-7e30-899e-4e2fc854f56e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019f93bd-0723-7e30-899e-4e2fc854f56e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019f93bd-0723-7e30-899e-4e2fc854f56e" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019f93bd-0723-7e30-899e-4e2fc854f56e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019f93bd-0723-7fad-b56c-f03489bd0874" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019f93bd-0723-7e30-899e-4e2fc854f56e" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019f93bd-0723-7fad-b56c-f03489bd0874" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_OtherRelatedPartyTransactionsWithTheCEOMember_019f93bd-0723-7267-bb09-a6589354b14f" xlink:href="nmrk-20260630.xsd#nmrk_OtherRelatedPartyTransactionsWithTheCEOMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019f93bd-0723-7fad-b56c-f03489bd0874" xlink:to="loc_nmrk_OtherRelatedPartyTransactionsWithTheCEOMember_019f93bd-0723-7267-bb09-a6589354b14f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019f93bd-0723-74f9-ac53-dd90f4f8c5f0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_019f93bd-0723-74f9-ac53-dd90f4f8c5f0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019f93bd-0723-7f2b-ace2-b0f25a1ad07d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_019f93bd-0723-7f2b-ace2-b0f25a1ad07d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharePrice_019f93bd-0723-7434-ab09-01d11b189dd1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_us-gaap_SharePrice_019f93bd-0723-7434-ab09-01d11b189dd1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019f93bd-0723-7afb-8192-1c64b4b33d84" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019f93bd-0723-7afb-8192-1c64b4b33d84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionNumberOfSons_019f93bd-0723-7c37-b8d9-86bec9a2061a" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionNumberOfSons"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_nmrk_RelatedPartyTransactionNumberOfSons_019f93bd-0723-7c37-b8d9-86bec9a2061a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionEmployeeCompensationAnnualCompensation_019f93bd-0723-7a1d-a78c-9223ae50d896" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionEmployeeCompensationAnnualCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7dae-88d6-2e977ae21a90" xlink:to="loc_nmrk_RelatedPartyTransactionEmployeeCompensationAnnualCompensation_019f93bd-0723-7a1d-a78c-9223ae50d896" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsOtherRelatedPartyTransactionsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsOtherRelatedPartyTransactionsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsOtherRelatedPartyTransactionsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7374-a0a9-6c44901c4745" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7374-a0a9-6c44901c4745" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7374-a0a9-6c44901c4745_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7374-a0a9-6c44901c4745" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7374-a0a9-6c44901c4745_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7608-b346-7a56e5e6f8a8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7374-a0a9-6c44901c4745" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7608-b346-7a56e5e6f8a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-79d1-baef-fe16a0574ad4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7608-b346-7a56e5e6f8a8" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-79d1-baef-fe16a0574ad4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_019e4774-a67d-766a-bde4-7a6760dc53e8" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:to="loc_us-gaap_CreditFacilityAxis_019e4774-a67d-766a-bde4-7a6760dc53e8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67d-766a-bde4-7a6760dc53e8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67d-766a-bde4-7a6760dc53e8" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67d-766a-bde4-7a6760dc53e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_019e4774-a67d-7b57-8b2a-ff732f4e912b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_019e4774-a67d-766a-bde4-7a6760dc53e8" xlink:to="loc_us-gaap_CreditFacilityDomain_019e4774-a67d-7b57-8b2a-ff732f4e912b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CantorCreditAgreementMember_019e4774-a67d-7225-b99d-10cd53c74ade" xlink:href="nmrk-20260630.xsd#nmrk_CantorCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a67d-7b57-8b2a-ff732f4e912b" xlink:to="loc_nmrk_CantorCreditAgreementMember_019e4774-a67d-7225-b99d-10cd53c74ade" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67d-7886-b235-124da1be1967" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_019e4774-a67d-7b57-8b2a-ff732f4e912b" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_019e4774-a67d-7886-b235-124da1be1967" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7143-9426-acb316de9941" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7143-9426-acb316de9941" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7143-9426-acb316de9941_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7143-9426-acb316de9941" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7143-9426-acb316de9941_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7761-a64f-be781135cb01" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7143-9426-acb316de9941" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7761-a64f-be781135cb01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_019e4774-a67d-71dd-954d-a58198db636d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7761-a64f-be781135cb01" xlink:to="loc_us-gaap_LineOfCreditMember_019e4774-a67d-71dd-954d-a58198db636d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7a40-a185-3abc89ee0ba6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7a40-a185-3abc89ee0ba6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7a40-a185-3abc89ee0ba6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7a40-a185-3abc89ee0ba6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7a40-a185-3abc89ee0ba6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7158-af71-4a9db5679cd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-7a40-a185-3abc89ee0ba6" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7158-af71-4a9db5679cd7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CantorCreditAgreementMember_019e4774-a67d-7349-900e-bc49ca964b8e" xlink:href="nmrk-20260630.xsd#nmrk_CantorCreditAgreementMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-7158-af71-4a9db5679cd7" xlink:to="loc_nmrk_CantorCreditAgreementMember_019e4774-a67d-7349-900e-bc49ca964b8e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_019e4774-a67d-7e93-b151-2bec89241307" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7399-8fe7-b95c8aff0561" xlink:to="loc_dei_LegalEntityAxis_019e4774-a67d-7e93-b151-2bec89241307" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e4774-a67d-7e93-b151-2bec89241307_default" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_019e4774-a67d-7e93-b151-2bec89241307" xlink:to="loc_dei_EntityDomain_019e4774-a67d-7e93-b151-2bec89241307_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_019e4774-a67d-7d85-8f72-4bd537c487d9" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_019e4774-a67d-7e93-b151-2bec89241307" xlink:to="loc_dei_EntityDomain_019e4774-a67d-7d85-8f72-4bd537c487d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CantorMember_019e4774-a67d-7f00-af20-058ff0d71852" xlink:href="nmrk-20260630.xsd#nmrk_CantorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_019e4774-a67d-7d85-8f72-4bd537c487d9" xlink:to="loc_nmrk_CantorMember_019e4774-a67d-7f00-af20-058ff0d71852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_019e4774-a67d-7b0b-9d65-6cd809aa59f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_019e4774-a67d-7b0b-9d65-6cd809aa59f5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableOtherCurrent_019e4774-a67d-7fc2-8437-904793d04754" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableOtherCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_AccountsPayableOtherCurrent_019e4774-a67d-7fc2-8437-904793d04754" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionMaximumAmountPerLoan_019e4774-a67d-798d-9926-b44af10a0adb" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionMaximumAmountPerLoan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_nmrk_RelatedPartyTransactionMaximumAmountPerLoan_019e4774-a67d-798d-9926-b44af10a0adb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionLimitOnLoanNotYetAcquiredOrSold_019e4774-a67d-749f-b3f8-7d915950eb65" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionLimitOnLoanNotYetAcquiredOrSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_nmrk_RelatedPartyTransactionLimitOnLoanNotYetAcquiredOrSold_019e4774-a67d-749f-b3f8-7d915950eb65" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionLimitOnLoanOutstanding_019e4774-a67d-7471-a064-dc2c16f64416" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionLimitOnLoanOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_nmrk_RelatedPartyTransactionLimitOnLoanOutstanding_019e4774-a67d-7471-a064-dc2c16f64416" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4774-a67d-7de8-9c26-2c91ad71b55a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_019e4774-a67d-7de8-9c26-2c91ad71b55a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a67d-7825-9932-788805f5e9c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_019e4774-a67d-7825-9932-788805f5e9c6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_019e4774-a67d-74d7-b86b-f4d6e0b01637" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_LongTermDebt_019e4774-a67d-74d7-b86b-f4d6e0b01637" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionDueFromToRelatedPartyPercentageFromSale_019e4774-a67d-744a-9d74-d948223b3a67" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionDueFromToRelatedPartyPercentageFromSale"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_nmrk_RelatedPartyTransactionDueFromToRelatedPartyPercentageFromSale_019e4774-a67d-744a-9d74-d948223b3a67" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetRentableArea_019e4774-a67d-73b1-8b01-7de783b1e086" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetRentableArea"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_us-gaap_NetRentableArea_019e4774-a67d-73b1-8b01-7de783b1e086" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LessorOperatingSubleaseLeasePayment_019e4774-a67d-72aa-a12b-e6f6b2ed9b3d" xlink:href="nmrk-20260630.xsd#nmrk_LessorOperatingSubleaseLeasePayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_nmrk_LessorOperatingSubleaseLeasePayment_019e4774-a67d-72aa-a12b-e6f6b2ed9b3d" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LessorOperatingSubleaseLeaseReceived_019e4774-a67d-7cbe-9735-8b404f0fa8cd" xlink:href="nmrk-20260630.xsd#nmrk_LessorOperatingSubleaseLeaseReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7e1c-b76b-975e5a9c2533" xlink:to="loc_nmrk_LessorOperatingSubleaseLeaseReceived_019e4774-a67d-7cbe-9735-8b404f0fa8cd" xlink:type="arc" order="11"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsServicesAgreementwithCantorFitzgeraldEuropeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsServicesAgreementwithCantorFitzgeraldEuropeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsServicesAgreementwithCantorFitzgeraldEuropeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7b0f-86b8-f509e0644bf5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7b46-b918-e6736aade458" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7b0f-86b8-f509e0644bf5" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7b46-b918-e6736aade458" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-781a-a83c-9eac60640036" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7b46-b918-e6736aade458" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-781a-a83c-9eac60640036" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-781a-a83c-9eac60640036_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-781a-a83c-9eac60640036" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-781a-a83c-9eac60640036_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7b9e-b033-bdceff4c305d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-781a-a83c-9eac60640036" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7b9e-b033-bdceff4c305d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RealEstateInvestmentBankingServicesReimbursementPremiumMember_019e4774-a67d-7196-836b-173b7d3be349" xlink:href="nmrk-20260630.xsd#nmrk_RealEstateInvestmentBankingServicesReimbursementPremiumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7b9e-b033-bdceff4c305d" xlink:to="loc_nmrk_RealEstateInvestmentBankingServicesReimbursementPremiumMember_019e4774-a67d-7196-836b-173b7d3be349" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RealEstateInvestmentBankingServicesAdditionalPremiumMember_019e4774-a67d-7de6-b9e0-831188c3957f" xlink:href="nmrk-20260630.xsd#nmrk_RealEstateInvestmentBankingServicesAdditionalPremiumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7b9e-b033-bdceff4c305d" xlink:to="loc_nmrk_RealEstateInvestmentBankingServicesAdditionalPremiumMember_019e4774-a67d-7de6-b9e0-831188c3957f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a67d-7b0b-a80e-3dac64e79423" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7b46-b918-e6736aade458" xlink:to="loc_srt_RangeAxis_019e4774-a67d-7b0b-a80e-3dac64e79423" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-7b0b-a80e-3dac64e79423_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7b0b-a80e-3dac64e79423" xlink:to="loc_srt_RangeMember_019e4774-a67d-7b0b-a80e-3dac64e79423_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-784e-ba59-90b5b2692ca1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7b0b-a80e-3dac64e79423" xlink:to="loc_srt_RangeMember_019e4774-a67d-784e-ba59-90b5b2692ca1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a67d-728e-9afe-297ea1081de0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-784e-ba59-90b5b2692ca1" xlink:to="loc_srt_MinimumMember_019e4774-a67d-728e-9afe-297ea1081de0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a67d-7b9b-9750-1dab42289366" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-784e-ba59-90b5b2692ca1" xlink:to="loc_srt_MaximumMember_019e4774-a67d-7b9b-9750-1dab42289366" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionRate_019e4774-a67d-7b03-aeb7-058a09cdd9ae" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7b0f-86b8-f509e0644bf5" xlink:to="loc_us-gaap_RelatedPartyTransactionRate_019e4774-a67d-7b03-aeb7-058a09cdd9ae" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsJointCapitalRaisingandAdvisoryServicesAuthorizationwithCFCoDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsJointCapitalRaisingandAdvisoryServicesAuthorizationwithCFCoDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsJointCapitalRaisingandAdvisoryServicesAuthorizationwithCFCoDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7c3e-b33c-a951b6d21040" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7469-b88a-9ac8804f808c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7c3e-b33c-a951b6d21040" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7469-b88a-9ac8804f808c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-73ad-b28a-3588f1b2b126" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7469-b88a-9ac8804f808c" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-73ad-b28a-3588f1b2b126" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-73ad-b28a-3588f1b2b126_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-73ad-b28a-3588f1b2b126" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-73ad-b28a-3588f1b2b126_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-72b4-9782-39aa9da33c32" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-73ad-b28a-3588f1b2b126" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-72b4-9782-39aa9da33c32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-76b8-abd6-82cc64b911aa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-72b4-9782-39aa9da33c32" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-76b8-abd6-82cc64b911aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7eae-9204-e2b18f0c12a1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7469-b88a-9ac8804f808c" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7eae-9204-e2b18f0c12a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7eae-9204-e2b18f0c12a1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7eae-9204-e2b18f0c12a1" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7eae-9204-e2b18f0c12a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-757c-89aa-397c9f94e89f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7eae-9204-e2b18f0c12a1" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-757c-89aa-397c9f94e89f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_JointCapitalRaisingAndAdvisoryServicesAuthorizationMember_019e4774-a67d-7144-80ec-9f3e16d814f6" xlink:href="nmrk-20260630.xsd#nmrk_JointCapitalRaisingAndAdvisoryServicesAuthorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-757c-89aa-397c9f94e89f" xlink:to="loc_nmrk_JointCapitalRaisingAndAdvisoryServicesAuthorizationMember_019e4774-a67d-7144-80ec-9f3e16d814f6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAdvisoryFeeMinimum_019e4774-a67d-7c5e-bdfe-080029615e49" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAdvisoryFeeMinimum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7c3e-b33c-a951b6d21040" xlink:to="loc_nmrk_RelatedPartyTransactionAdvisoryFeeMinimum_019e4774-a67d-7c5e-bdfe-080029615e49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAdvisoryFeeGrossProceedsPercentage_019e4774-a67d-7d63-a026-77d5209d4834" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAdvisoryFeeGrossProceedsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7c3e-b33c-a951b6d21040" xlink:to="loc_nmrk_RelatedPartyTransactionAdvisoryFeeGrossProceedsPercentage_019e4774-a67d-7d63-a026-77d5209d4834" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionAdvisoryFeeMaximum_019e4774-a67d-7617-8294-519592f6cb16" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionAdvisoryFeeMaximum"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7c3e-b33c-a951b6d21040" xlink:to="loc_nmrk_RelatedPartyTransactionAdvisoryFeeMaximum_019e4774-a67d-7617-8294-519592f6cb16" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsMarketMakingRegistrationStatementforCFCoReferralPaymentandPlacementAgentAuthorizationwithCFCoDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsMarketMakingRegistrationStatementforCFCoReferralPaymentandPlacementAgentAuthorizationwithCFCoDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsMarketMakingRegistrationStatementforCFCoReferralPaymentandPlacementAgentAuthorizationwithCFCoDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7d53-9125-0b98ab95e79e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7682-8144-d9454faecb89" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7d53-9125-0b98ab95e79e" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7682-8144-d9454faecb89" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7911-a08c-acd4020c0134" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7682-8144-d9454faecb89" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7911-a08c-acd4020c0134" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7911-a08c-acd4020c0134_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7911-a08c-acd4020c0134" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7911-a08c-acd4020c0134_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7eb0-9637-ed6ce536d8e4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7911-a08c-acd4020c0134" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7eb0-9637-ed6ce536d8e4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-78f5-9d9b-aefe6bfe2766" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7eb0-9637-ed6ce536d8e4" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-78f5-9d9b-aefe6bfe2766" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-795a-92c0-8b77a5efdf55" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7682-8144-d9454faecb89" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-795a-92c0-8b77a5efdf55" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-795a-92c0-8b77a5efdf55_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-795a-92c0-8b77a5efdf55" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-795a-92c0-8b77a5efdf55_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-72cd-8f7b-b7858adff93c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-795a-92c0-8b77a5efdf55" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-72cd-8f7b-b7858adff93c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_SevenPointFiveZeroZeroPercentSeniorNotesMember_019e4774-a67d-7a7a-bade-1decd0411e15" xlink:href="nmrk-20260630.xsd#nmrk_SevenPointFiveZeroZeroPercentSeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-72cd-8f7b-b7858adff93c" xlink:to="loc_nmrk_SevenPointFiveZeroZeroPercentSeniorNotesMember_019e4774-a67d-7a7a-bade-1decd0411e15" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a67d-7ada-a4c8-abe01a456c64" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7d53-9125-0b98ab95e79e" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a67d-7ada-a4c8-abe01a456c64" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionReferralFeePercentage_019e4774-a67d-7e21-babe-0dce9b6a71e7" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionReferralFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7d53-9125-0b98ab95e79e" xlink:to="loc_nmrk_RelatedPartyTransactionReferralFeePercentage_019e4774-a67d-7e21-babe-0dce9b6a71e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RelatedPartyTransactionReferralFeeAmountsReceived_019e4774-a67d-7b29-8791-879901ab5959" xlink:href="nmrk-20260630.xsd#nmrk_RelatedPartyTransactionReferralFeeAmountsReceived"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7d53-9125-0b98ab95e79e" xlink:to="loc_nmrk_RelatedPartyTransactionReferralFeeAmountsReceived_019e4774-a67d-7b29-8791-879901ab5959" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsCantorRightstoPurchaseCantorUnitsfromNewmarkHoldingsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsCantorRightstoPurchaseCantorUnitsfromNewmarkHoldingsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsCantorRightstoPurchaseCantorUnitsfromNewmarkHoldingsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7ebb-a089-7b4c2bb68ee7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7ebb-a089-7b4c2bb68ee7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-7ebb-a089-7b4c2bb68ee7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7ebb-a089-7b4c2bb68ee7" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-7ebb-a089-7b4c2bb68ee7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-776f-81ad-802b1b462532" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7ebb-a089-7b4c2bb68ee7" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-776f-81ad-802b1b462532" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_019e4774-a67d-7f68-aabc-b4db0c1bab0a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-776f-81ad-802b1b462532" xlink:to="loc_us-gaap_CommonStockMember_019e4774-a67d-7f68-aabc-b4db0c1bab0a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a67d-7905-9d61-21d9a146598b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-776f-81ad-802b1b462532" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a67d-7905-9d61-21d9a146598b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7336-a5ab-6f158ad3aa81" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7336-a5ab-6f158ad3aa81" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7336-a5ab-6f158ad3aa81_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7336-a5ab-6f158ad3aa81" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7336-a5ab-6f158ad3aa81_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-712c-b2c2-7f7daebbd667" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7336-a5ab-6f158ad3aa81" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-712c-b2c2-7f7daebbd667" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a67d-7ccd-ad83-7af40605cf28" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-712c-b2c2-7f7daebbd667" xlink:to="loc_srt_ParentCompanyMember_019e4774-a67d-7ccd-ad83-7af40605cf28" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7f0b-a0fd-2880df9a6107" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7f0b-a0fd-2880df9a6107" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-7f0b-a0fd-2880df9a6107_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7f0b-a0fd-2880df9a6107" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-7f0b-a0fd-2880df9a6107_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-716b-adf6-6a0c51e1ae56" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7f0b-a0fd-2880df9a6107" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-716b-adf6-6a0c51e1ae56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnerMember_019e4774-a67d-7a84-83dd-5320e4382dbb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-716b-adf6-6a0c51e1ae56" xlink:to="loc_us-gaap_GeneralPartnerMember_019e4774-a67d-7a84-83dd-5320e4382dbb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnerMember_019e4774-a67d-719a-a8f4-9dd0d0aefd57" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LimitedPartnerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-716b-adf6-6a0c51e1ae56" xlink:to="loc_us-gaap_LimitedPartnerMember_019e4774-a67d-719a-a8f4-9dd0d0aefd57" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-785d-89fc-f104823ca53d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-785d-89fc-f104823ca53d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-785d-89fc-f104823ca53d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-785d-89fc-f104823ca53d" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-785d-89fc-f104823ca53d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-775b-b932-a692df229bf9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-785d-89fc-f104823ca53d" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-775b-b932-a692df229bf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-7749-9bff-000f9684aadb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-775b-b932-a692df229bf9" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-7749-9bff-000f9684aadb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a67d-74e0-ae3b-74de7ee05f97" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-77dc-bed7-b27620005e29" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a67d-74e0-ae3b-74de7ee05f97" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-74e0-ae3b-74de7ee05f97_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a67d-74e0-ae3b-74de7ee05f97" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-74e0-ae3b-74de7ee05f97_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-78d0-8f6b-de624bf4cb8e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a67d-74e0-ae3b-74de7ee05f97" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-78d0-8f6b-de624bf4cb8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ExchangeableLimitedPartnershipInterestsMember_019e4774-a67d-70c4-8db8-c31489e5c85f" xlink:href="nmrk-20260630.xsd#nmrk_ExchangeableLimitedPartnershipInterestsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-78d0-8f6b-de624bf4cb8e" xlink:to="loc_nmrk_ExchangeableLimitedPartnershipInterestsMember_019e4774-a67d-70c4-8db8-c31489e5c85f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsExchangeRatio_019e4774-a67d-7a44-9433-b36183377563" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsExchangeRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_nmrk_LimitedPartnershipUnitsExchangeRatio_019e4774-a67d-7a44-9433-b36183377563" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019e4774-a67d-7da2-9036-58385d2d70be" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_019e4774-a67d-7da2-9036-58385d2d70be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019e4774-a67d-76ea-9916-06f69b93a5bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019e4774-a67d-76ea-9916-06f69b93a5bb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019e4774-a67d-7d56-85a1-ff57ec4e5fba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_019e4774-a67d-7d56-85a1-ff57ec4e5fba" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromPartnershipContribution_019e4774-a67d-7a0d-b5d6-9c2fb8b050bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromPartnershipContribution"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_us-gaap_ProceedsFromPartnershipContribution_019e4774-a67d-7a0d-b5d6-9c2fb8b050bf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_TaxReceivableAgreementCashSavingsPercentage_019e4774-a67d-751a-9a3d-21d881626cc8" xlink:href="nmrk-20260630.xsd#nmrk_TaxReceivableAgreementCashSavingsPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_nmrk_TaxReceivableAgreementCashSavingsPercentage_019e4774-a67d-751a-9a3d-21d881626cc8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_TaxReceivableAgreementAssetNoncurrent_019e4774-a67d-7394-a0e0-649298ac88b8" xlink:href="nmrk-20260630.xsd#nmrk_TaxReceivableAgreementAssetNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_nmrk_TaxReceivableAgreementAssetNoncurrent_019e4774-a67d-7394-a0e0-649298ac88b8" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_TaxReceivableAgreementLiabilityNoncurrent_019e4774-a67d-7a58-b197-4ef0081f7804" xlink:href="nmrk-20260630.xsd#nmrk_TaxReceivableAgreementLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_nmrk_TaxReceivableAgreementLiabilityNoncurrent_019e4774-a67d-7a58-b197-4ef0081f7804" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_019e4774-a67d-72d4-b40a-e41db59c2340" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-791d-b2e7-dda2f8114a0e" xlink:to="loc_us-gaap_GeneralPartnersCapitalAccountUnitsOutstanding_019e4774-a67d-72d4-b40a-e41db59c2340" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactions7500SeniorNotesDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactions7500SeniorNotesDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactions7500SeniorNotesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7244-8ecf-47a5352836fb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f71-9989-8eff13af8518" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7244-8ecf-47a5352836fb" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f71-9989-8eff13af8518" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-775b-a175-6bf1fddede7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f71-9989-8eff13af8518" xlink:to="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-775b-a175-6bf1fddede7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-775b-a175-6bf1fddede7e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-775b-a175-6bf1fddede7e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-775b-a175-6bf1fddede7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-753f-b385-2ff72f6ad597" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_019e4774-a67d-775b-a175-6bf1fddede7e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-753f-b385-2ff72f6ad597" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67d-7ba9-b782-942f3c33b01a" xlink:href="nmrk-20260630.xsd#nmrk_A7.500SeniorNotesDueJanuary122029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_019e4774-a67d-753f-b385-2ff72f6ad597" xlink:to="loc_nmrk_A7.500SeniorNotesDueJanuary122029Member_019e4774-a67d-7ba9-b782-942f3c33b01a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7b7a-bd3d-c578caf868dd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f71-9989-8eff13af8518" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7b7a-bd3d-c578caf868dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7b7a-bd3d-c578caf868dd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7b7a-bd3d-c578caf868dd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-7b7a-bd3d-c578caf868dd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-76c2-b84f-91905da0a6c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_019e4774-a67d-7b7a-bd3d-c578caf868dd" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-76c2-b84f-91905da0a6c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_019e4774-a67d-75cf-9821-2a37ee8cc5fd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_019e4774-a67d-76c2-b84f-91905da0a6c4" xlink:to="loc_us-gaap_SeniorNotesMember_019e4774-a67d-75cf-9821-2a37ee8cc5fd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_019e4774-a67d-7fa1-a107-020c4d3ab3b4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f71-9989-8eff13af8518" xlink:to="loc_srt_CounterpartyNameAxis_019e4774-a67d-7fa1-a107-020c4d3ab3b4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019e4774-a67d-7fa1-a107-020c4d3ab3b4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_019e4774-a67d-7fa1-a107-020c4d3ab3b4" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019e4774-a67d-7fa1-a107-020c4d3ab3b4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019e4774-a67d-77f3-a6c9-82774532eb35" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_019e4774-a67d-7fa1-a107-020c4d3ab3b4" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019e4774-a67d-77f3-a6c9-82774532eb35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CantorMember_019e4774-a67d-7935-9e12-8d0becb5700a" xlink:href="nmrk-20260630.xsd#nmrk_CantorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_019e4774-a67d-77f3-a6c9-82774532eb35" xlink:to="loc_nmrk_CantorMember_019e4774-a67d-7935-9e12-8d0becb5700a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7511-8266-deff2c0d753d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-7f71-9989-8eff13af8518" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7511-8266-deff2c0d753d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7511-8266-deff2c0d753d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7511-8266-deff2c0d753d" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-7511-8266-deff2c0d753d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-77de-98e9-fdda210ab30b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019e4774-a67d-7511-8266-deff2c0d753d" xlink:to="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-77de-98e9-fdda210ab30b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyMember_019e4774-a67d-7569-91b7-9fe3068578e3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019e4774-a67d-77de-98e9-fdda210ab30b" xlink:to="loc_us-gaap_RelatedPartyMember_019e4774-a67d-7569-91b7-9fe3068578e3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a67d-71a1-9489-c3e58f2cabcd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7244-8ecf-47a5352836fb" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_019e4774-a67d-71a1-9489-c3e58f2cabcd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_019e4774-a67d-7d80-8616-bd7c2ac1683e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7244-8ecf-47a5352836fb" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_019e4774-a67d-7d80-8616-bd7c2ac1683e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_019e4774-a67d-78bc-b173-016094107df4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7244-8ecf-47a5352836fb" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_019e4774-a67d-78bc-b173-016094107df4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019e4774-a67d-7689-8c09-0cc3ff26373c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7244-8ecf-47a5352836fb" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfLongTermDebt_019e4774-a67d-7689-8c09-0cc3ff26373c" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/RelatedPartyTransactionsServicesAgreementwithCantorFitzgeraldEuropefortheProvisionofRealEstateInvestmentBankingServicesDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#RelatedPartyTransactionsServicesAgreementwithCantorFitzgeraldEuropefortheProvisionofRealEstateInvestmentBankingServicesDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/RelatedPartyTransactionsServicesAgreementwithCantorFitzgeraldEuropefortheProvisionofRealEstateInvestmentBankingServicesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7a0e-a458-78378fdc950c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-78e7-b6e0-1bad94fa2f5a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7a0e-a458-78378fdc950c" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-78e7-b6e0-1bad94fa2f5a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7341-bfa1-9cc8417b2fce" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-78e7-b6e0-1bad94fa2f5a" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7341-bfa1-9cc8417b2fce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7341-bfa1-9cc8417b2fce_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7341-bfa1-9cc8417b2fce" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7341-bfa1-9cc8417b2fce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7ad4-ab23-98968e3936bf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_019e4774-a67d-7341-bfa1-9cc8417b2fce" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7ad4-ab23-98968e3936bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RealEstateInvestmentBankingServicesReimbursementPremiumMember_019e4774-a67d-7c09-a373-7f9c648fc9ee" xlink:href="nmrk-20260630.xsd#nmrk_RealEstateInvestmentBankingServicesReimbursementPremiumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7ad4-ab23-98968e3936bf" xlink:to="loc_nmrk_RealEstateInvestmentBankingServicesReimbursementPremiumMember_019e4774-a67d-7c09-a373-7f9c648fc9ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RealEstateInvestmentBankingServicesAllocatedRevenueMember_019e4774-a67d-72e0-ab93-363e6d5b0921" xlink:href="nmrk-20260630.xsd#nmrk_RealEstateInvestmentBankingServicesAllocatedRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7ad4-ab23-98968e3936bf" xlink:to="loc_nmrk_RealEstateInvestmentBankingServicesAllocatedRevenueMember_019e4774-a67d-72e0-ab93-363e6d5b0921" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_RealEstateInvestmentBankingServicesAdditionalPremiumMember_019e4774-a67d-76ab-af36-86dbf86d1f25" xlink:href="nmrk-20260630.xsd#nmrk_RealEstateInvestmentBankingServicesAdditionalPremiumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_019e4774-a67d-7ad4-ab23-98968e3936bf" xlink:to="loc_nmrk_RealEstateInvestmentBankingServicesAdditionalPremiumMember_019e4774-a67d-76ab-af36-86dbf86d1f25" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a67d-7087-85ae-b8c216d7ae81" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_019e4774-a67d-78e7-b6e0-1bad94fa2f5a" xlink:to="loc_srt_RangeAxis_019e4774-a67d-7087-85ae-b8c216d7ae81" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-7087-85ae-b8c216d7ae81_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7087-85ae-b8c216d7ae81" xlink:to="loc_srt_RangeMember_019e4774-a67d-7087-85ae-b8c216d7ae81_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a67d-759a-b6d5-560a92837a94" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a67d-7087-85ae-b8c216d7ae81" xlink:to="loc_srt_RangeMember_019e4774-a67d-759a-b6d5-560a92837a94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a67d-7902-9508-0a9f02cd7396" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-759a-b6d5-560a92837a94" xlink:to="loc_srt_MinimumMember_019e4774-a67d-7902-9508-0a9f02cd7396" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a67d-7702-8d8e-0f60a6405b22" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a67d-759a-b6d5-560a92837a94" xlink:to="loc_srt_MaximumMember_019e4774-a67d-7702-8d8e-0f60a6405b22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionRate_019e4774-a67d-72f0-ac07-2bc75e39b91c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_019e4774-a67d-7a0e-a458-78378fdc950c" xlink:to="loc_us-gaap_RelatedPartyTransactionRate_019e4774-a67d-72f0-ac07-2bc75e39b91c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_019e4774-a67d-7ba2-9c3d-bbce43ebc135" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_us-gaap_PlanNameAxis_019e4774-a67d-7ba2-9c3d-bbce43ebc135" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019e4774-a67d-7ba2-9c3d-bbce43ebc135_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_019e4774-a67d-7ba2-9c3d-bbce43ebc135" xlink:to="loc_us-gaap_PlanNameDomain_019e4774-a67d-7ba2-9c3d-bbce43ebc135_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_019e4774-a67d-78a5-ad79-5dfb0046ea5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_019e4774-a67d-7ba2-9c3d-bbce43ebc135" xlink:to="loc_us-gaap_PlanNameDomain_019e4774-a67d-78a5-ad79-5dfb0046ea5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LongTermEquityIncentivePlanMember_019e4774-a67d-702d-a384-9234d14f5a03" xlink:href="nmrk-20260630.xsd#nmrk_LongTermEquityIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_019e4774-a67d-78a5-ad79-5dfb0046ea5f" xlink:to="loc_nmrk_LongTermEquityIncentivePlanMember_019e4774-a67d-702d-a384-9234d14f5a03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7cfa-b756-90ae6fe53da7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7cfa-b756-90ae6fe53da7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-7cfa-b756-90ae6fe53da7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7cfa-b756-90ae6fe53da7" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-7cfa-b756-90ae6fe53da7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-78dc-9166-59ed515866ed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a67d-7cfa-b756-90ae6fe53da7" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-78dc-9166-59ed515866ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a67d-7c03-95e0-7045b4ffbe6d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a67d-78dc-9166-59ed515866ed" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a67d-7c03-95e0-7045b4ffbe6d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7d74-a142-d347933720e6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7d74-a142-d347933720e6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7d74-a142-d347933720e6_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7d74-a142-d347933720e6" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7d74-a142-d347933720e6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7424-a9bc-4a15d5874775" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a67d-7d74-a142-d347933720e6" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7424-a9bc-4a15d5874775" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NewmarkHoldingsLimitedPartnershipMember_019e4774-a67d-746c-b0f7-57c0da62fbde" xlink:href="nmrk-20260630.xsd#nmrk_NewmarkHoldingsLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7424-a9bc-4a15d5874775" xlink:to="loc_nmrk_NewmarkHoldingsLimitedPartnershipMember_019e4774-a67d-746c-b0f7-57c0da62fbde" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a67d-74e0-9493-8afaf0c9d84d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a67d-7424-a9bc-4a15d5874775" xlink:to="loc_srt_ParentCompanyMember_019e4774-a67d-74e0-9493-8afaf0c9d84d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalUnitsByClassAxis_019e4774-a67d-7511-b7b1-4a7a0449f22c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalUnitsByClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_us-gaap_CapitalUnitsByClassAxis_019e4774-a67d-7511-b7b1-4a7a0449f22c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalUnitClassDomain_019e4774-a67d-7511-b7b1-4a7a0449f22c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalUnitClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CapitalUnitsByClassAxis_019e4774-a67d-7511-b7b1-4a7a0449f22c" xlink:to="loc_us-gaap_CapitalUnitClassDomain_019e4774-a67d-7511-b7b1-4a7a0449f22c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalUnitClassDomain_019e4774-a67d-7594-89a1-6dabb03ec6c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CapitalUnitClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CapitalUnitsByClassAxis_019e4774-a67d-7511-b7b1-4a7a0449f22c" xlink:to="loc_us-gaap_CapitalUnitClassDomain_019e4774-a67d-7594-89a1-6dabb03ec6c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NonDistributionEarningUnitsMember_019e4774-a67d-7de6-85c8-fd8b8a191ec2" xlink:href="nmrk-20260630.xsd#nmrk_NonDistributionEarningUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CapitalUnitClassDomain_019e4774-a67d-7594-89a1-6dabb03ec6c5" xlink:to="loc_nmrk_NonDistributionEarningUnitsMember_019e4774-a67d-7de6-85c8-fd8b8a191ec2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7c8d-9f95-4afb136b2dad" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7c8d-9f95-4afb136b2dad" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-7c8d-9f95-4afb136b2dad_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7c8d-9f95-4afb136b2dad" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-7c8d-9f95-4afb136b2dad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-78b0-8d22-21f02d7360bb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a67d-7c8d-9f95-4afb136b2dad" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-78b0-8d22-21f02d7360bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a67d-7e00-9229-b067372a6c51" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a67d-78b0-8d22-21f02d7360bb" xlink:to="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a67d-7e00-9229-b067372a6c51" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a67d-7048-bd54-77f897d5a5a4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a67d-7048-bd54-77f897d5a5a4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-7048-bd54-77f897d5a5a4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a67d-7048-bd54-77f897d5a5a4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a67d-7048-bd54-77f897d5a5a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7198-b0e8-f9453cff4c22" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a67d-7048-bd54-77f897d5a5a4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7198-b0e8-f9453cff4c22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-76a0-a8b5-1cc5648a18ff" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7198-b0e8-f9453cff4c22" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-76a0-a8b5-1cc5648a18ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e6002-27b1-7a76-bfcf-f9aba8896e36" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a67d-7ff5-ae46-37aa496b7b5b" xlink:to="loc_srt_RangeAxis_019e6002-27b1-7a76-bfcf-f9aba8896e36" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e6002-27b1-7a76-bfcf-f9aba8896e36_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e6002-27b1-7a76-bfcf-f9aba8896e36" xlink:to="loc_srt_RangeMember_019e6002-27b1-7a76-bfcf-f9aba8896e36_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e6002-27b1-7eac-9212-138ad6437f76" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e6002-27b1-7a76-bfcf-f9aba8896e36" xlink:to="loc_srt_RangeMember_019e6002-27b1-7eac-9212-138ad6437f76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e6002-27b1-7a04-babc-aac73d43b47e" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e6002-27b1-7eac-9212-138ad6437f76" xlink:to="loc_srt_MaximumMember_019e6002-27b1-7a04-babc-aac73d43b47e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019e4774-a73f-7cbc-9326-15ee64f712f1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_019e4774-a73f-7cbc-9326-15ee64f712f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_019e4774-a73f-7b5f-9d42-100843402a8c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_019e4774-a73f-7b5f-9d42-100843402a8c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesRegistered_019e4774-a73f-7fcc-992a-160064c76008" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesRegistered"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesRegistered_019e4774-a73f-7fcc-992a-160064c76008" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesGranted_019e4774-a73f-7739-86e0-3638ac58664d" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesGranted_019e4774-a73f-7739-86e0-3638ac58664d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019e4774-a73f-73f8-b256-7594d4d30530" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_019e4774-a73f-73f8-b256-7594d4d30530" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsExchangeRatio_019e4774-a73f-7c17-bc65-0ff537a3270f" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsExchangeRatio"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_nmrk_LimitedPartnershipUnitsExchangeRatio_019e4774-a73f-7c17-bc65-0ff537a3270f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019e4774-a73f-79b3-9c3b-b323bb08117a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019e4774-a73f-79b3-9c3b-b323bb08117a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_019e4774-a73f-70c6-8c5d-ae8193fef41d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_019e4774-a73f-70c6-8c5d-ae8193fef41d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested_019e4774-a73f-781b-b4a5-5a132c016b54" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested_019e4774-a73f-781b-b4a5-5a132c016b54" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_019e4774-a73f-7c01-993d-3bce2ce12e79" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_019e4774-a73f-7c01-993d-3bce2ce12e79" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019e4774-a73f-7433-99e2-d15e4d315d6b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_019e4774-a73f-7433-99e2-d15e4d315d6b" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4774-a73f-79ac-81ce-acd1eee253e6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4774-a73f-79ac-81ce-acd1eee253e6" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019e4774-a73f-763a-91e8-e7747817b503" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_019e4774-a73f-763a-91e8-e7747817b503" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_019e4774-a73f-7398-82a9-3b275f976898" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_019e4774-a73f-7398-82a9-3b275f976898" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CommonStockConversionForEachRestrictedStockUnitSettled_019e4774-a73f-7426-ad19-07818e89790a" xlink:href="nmrk-20260630.xsd#nmrk_CommonStockConversionForEachRestrictedStockUnitSettled"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7b05-8595-d73e58d6869e" xlink:to="loc_nmrk_CommonStockConversionForEachRestrictedStockUnitSettled_019e4774-a73f-7426-ad19-07818e89790a" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofCompensationExpenseRelatedtoLimitedPartnershipUnitsandRestrictedStockUnitsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofCompensationExpenseRelatedtoLimitedPartnershipUnitsandRestrictedStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofCompensationExpenseRelatedtoLimitedPartnershipUnitsandRestrictedStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-76f1-87f5-9a15f3715da2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-76f1-87f5-9a15f3715da2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7f7d-9a71-f61db51d9da5" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-76f1-87f5-9a15f3715da2" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7f7d-9a71-f61db51d9da5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7f7d-9a71-f61db51d9da5_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7f7d-9a71-f61db51d9da5" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7f7d-9a71-f61db51d9da5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7b1a-9622-e2211d5e735b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7f7d-9a71-f61db51d9da5" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7b1a-9622-e2211d5e735b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a73f-7a99-b3f8-552e23fb50fa" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7b1a-9622-e2211d5e735b" xlink:to="loc_srt_ParentCompanyMember_019e4774-a73f-7a99-b3f8-552e23fb50fa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-70f2-9246-77122ee953c5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-76f1-87f5-9a15f3715da2" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-70f2-9246-77122ee953c5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-70f2-9246-77122ee953c5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-70f2-9246-77122ee953c5" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-70f2-9246-77122ee953c5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-737d-8855-3dd524d89609" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-70f2-9246-77122ee953c5" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-737d-8855-3dd524d89609" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-701b-b121-8b961f0424b8" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-737d-8855-3dd524d89609" xlink:to="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-701b-b121-8b961f0424b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a73f-7ab1-9509-fd80480839eb" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-76f1-87f5-9a15f3715da2" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a73f-7ab1-9509-fd80480839eb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7ab1-9509-fd80480839eb_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-7ab1-9509-fd80480839eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7ab1-9509-fd80480839eb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7c87-8288-d19d365a240d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-7ab1-9509-fd80480839eb" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7c87-8288-d19d365a240d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-7f6f-9811-b5c56ac54f1c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7c87-8288-d19d365a240d" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-7f6f-9811-b5c56ac54f1c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CommonStockExchangeabilityGrantedIssuedExpense_019e4774-a73f-7459-91b6-7b2e540bfb1f" xlink:href="nmrk-20260630.xsd#nmrk_CommonStockExchangeabilityGrantedIssuedExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:to="loc_nmrk_CommonStockExchangeabilityGrantedIssuedExpense_019e4774-a73f-7459-91b6-7b2e540bfb1f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019e4774-a73f-778b-b2c2-130e38b3aebf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeBenefitsAndShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:to="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019e4774-a73f-778b-b2c2-130e38b3aebf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4774-a73f-71bd-b88f-65076f23de0b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_019e4774-a73f-71bd-b88f-65076f23de0b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared_019e4774-a73f-7acc-8a8c-f551e014ad7e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:to="loc_us-gaap_DistributionMadeToLimitedPartnerCashDistributionsDeclared_019e4774-a73f-7acc-8a8c-f551e014ad7e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_EquityBasedCompensationAndAllocationOfNetIncomeToLimitedPartnershipUnitsAndFPUs_019e4774-a73f-7dd9-ac70-d1c5051f53b9" xlink:href="nmrk-20260630.xsd#nmrk_EquityBasedCompensationAndAllocationOfNetIncomeToLimitedPartnershipUnitsAndFPUs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76df-94b2-73c0b286c703" xlink:to="loc_nmrk_EquityBasedCompensationAndAllocationOfNetIncomeToLimitedPartnershipUnitsAndFPUs_019e4774-a73f-7dd9-ac70-d1c5051f53b9" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofActivityAssociatedwithLimitedPartnershipUnitsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofActivityAssociatedwithLimitedPartnershipUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofActivityAssociatedwithLimitedPartnershipUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76b7-a829-d046744bd2d0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7ce2-91d6-eddfb6653cfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76b7-a829-d046744bd2d0" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7ce2-91d6-eddfb6653cfe" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7432-98eb-dec92f67a2c1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7ce2-91d6-eddfb6653cfe" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7432-98eb-dec92f67a2c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7432-98eb-dec92f67a2c1_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7432-98eb-dec92f67a2c1" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7432-98eb-dec92f67a2c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7558-af97-ed91f9462c7b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7432-98eb-dec92f67a2c1" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7558-af97-ed91f9462c7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a73f-76d2-afa8-4a04d0eca8eb" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7558-af97-ed91f9462c7b" xlink:to="loc_srt_ParentCompanyMember_019e4774-a73f-76d2-afa8-4a04d0eca8eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_BGCHoldingsLimitedPartnershipMember_019e4774-a73f-7f1b-af9d-6dbaffe2483e" xlink:href="nmrk-20260630.xsd#nmrk_BGCHoldingsLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7558-af97-ed91f9462c7b" xlink:to="loc_nmrk_BGCHoldingsLimitedPartnershipMember_019e4774-a73f-7f1b-af9d-6dbaffe2483e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a73f-75b0-9d48-53902a06890a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7ce2-91d6-eddfb6653cfe" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a73f-75b0-9d48-53902a06890a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-75b0-9d48-53902a06890a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-75b0-9d48-53902a06890a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-75b0-9d48-53902a06890a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7429-b03d-0014310c9565" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-75b0-9d48-53902a06890a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7429-b03d-0014310c9565" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-772e-a9d1-98326d05de09" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7429-b03d-0014310c9565" xlink:to="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-772e-a9d1-98326d05de09" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusAxis_019e4774-a73f-7938-aba0-c09b09a20852" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7ce2-91d6-eddfb6653cfe" xlink:to="loc_us-gaap_GranteeStatusAxis_019e4774-a73f-7938-aba0-c09b09a20852" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_019e4774-a73f-7938-aba0-c09b09a20852_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_GranteeStatusAxis_019e4774-a73f-7938-aba0-c09b09a20852" xlink:to="loc_us-gaap_GranteeStatusDomain_019e4774-a73f-7938-aba0-c09b09a20852_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GranteeStatusDomain_019e4774-a73f-7344-991a-ef3759f593f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GranteeStatusDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_GranteeStatusAxis_019e4774-a73f-7938-aba0-c09b09a20852" xlink:to="loc_us-gaap_GranteeStatusDomain_019e4774-a73f-7344-991a-ef3759f593f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_019e4774-a73f-7bc9-ba46-ea47cc6ed37c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedPaymentArrangementEmployeeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GranteeStatusDomain_019e4774-a73f-7344-991a-ef3759f593f3" xlink:to="loc_us-gaap_ShareBasedPaymentArrangementEmployeeMember_019e4774-a73f-7bc9-ba46-ea47cc6ed37c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-7da2-b34a-c8f0e6920e94" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76b7-a829-d046744bd2d0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-7da2-b34a-c8f0e6920e94" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019e4774-a73f-7bbf-8026-63bfce4b6c5f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-7da2-b34a-c8f0e6920e94" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019e4774-a73f-7bbf-8026-63bfce4b6c5f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_019e4774-a73f-73bd-945d-b3aaa8ea7028" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-7da2-b34a-c8f0e6920e94" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_019e4774-a73f-73bd-945d-b3aaa8ea7028" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentRedeemedExchanged_019e4774-a73f-74c8-b4b5-f9d7bfdb41a8" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentRedeemedExchanged"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-7da2-b34a-c8f0e6920e94" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentRedeemedExchanged_019e4774-a73f-74c8-b4b5-f9d7bfdb41a8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019e4774-a73f-7857-aed3-0283b29ec8fa" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-7da2-b34a-c8f0e6920e94" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019e4774-a73f-7857-aed3-0283b29ec8fa" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019e4774-a73f-7d83-8e24-ce9db8cfe268" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ExchangeableUnits_019e4774-a73f-7da1-bf61-d79771c3ce0a" xlink:href="nmrk-20260630.xsd#nmrk_ExchangeableUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76b7-a829-d046744bd2d0" xlink:to="loc_nmrk_ExchangeableUnits_019e4774-a73f-7da1-bf61-d79771c3ce0a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ExchangeablePartnershipUnits_019e4774-a73f-7409-ac97-057da5bc39a1" xlink:href="nmrk-20260630.xsd#nmrk_ExchangeablePartnershipUnits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-76b7-a829-d046744bd2d0" xlink:to="loc_nmrk_ExchangeablePartnershipUnits_019e4774-a73f-7409-ac97-057da5bc39a1" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofUnitsRedeemedinConnectionwithIssuanceofClassACommonStockDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofUnitsRedeemedinConnectionwithIssuanceofClassACommonStockDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofUnitsRedeemedinConnectionwithIssuanceofClassACommonStockDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7acf-b1e0-b71bc4bf2c16" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7791-8117-8e8a0c3871f2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7acf-b1e0-b71bc4bf2c16" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7791-8117-8e8a0c3871f2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7103-ba8f-0fd15ae32bcc" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7791-8117-8e8a0c3871f2" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7103-ba8f-0fd15ae32bcc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7103-ba8f-0fd15ae32bcc_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7103-ba8f-0fd15ae32bcc" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7103-ba8f-0fd15ae32bcc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-70da-ba93-05d85de2c1be" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7103-ba8f-0fd15ae32bcc" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-70da-ba93-05d85de2c1be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a73f-7a1f-b070-1138aba40bab" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-70da-ba93-05d85de2c1be" xlink:to="loc_srt_ParentCompanyMember_019e4774-a73f-7a1f-b070-1138aba40bab" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardUnitsRedeemed_019e4774-a73f-7dcc-b35f-f7121bd93ddd" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardUnitsRedeemed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7acf-b1e0-b71bc4bf2c16" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardUnitsRedeemed_019e4774-a73f-7dcc-b35f-f7121bd93ddd" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofLimitedPartnershipUnitswithaPostTerminationPayoutDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofLimitedPartnershipUnitswithaPostTerminationPayoutDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofLimitedPartnershipUnitswithaPostTerminationPayoutDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7e20-a4c8-34bd9573e57f" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-75a9-ba65-f716bcca5ebd" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7e20-a4c8-34bd9573e57f" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-75a9-ba65-f716bcca5ebd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7075-a6e1-770951bad866" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-75a9-ba65-f716bcca5ebd" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7075-a6e1-770951bad866" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7075-a6e1-770951bad866_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7075-a6e1-770951bad866" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7075-a6e1-770951bad866_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7bdc-bb1a-bedf7e13732f" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7075-a6e1-770951bad866" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7bdc-bb1a-bedf7e13732f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_BGCHoldingPartnershipUnitsMember_019e4774-a73f-776a-b1fd-64df21abed03" xlink:href="nmrk-20260630.xsd#nmrk_BGCHoldingPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7bdc-bb1a-bedf7e13732f" xlink:to="loc_nmrk_BGCHoldingPartnershipUnitsMember_019e4774-a73f-776a-b1fd-64df21abed03" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a73f-78cd-b7bf-7e333e6e4369" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7bdc-bb1a-bedf7e13732f" xlink:to="loc_srt_ParentCompanyMember_019e4774-a73f-78cd-b7bf-7e333e6e4369" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NotionalValueOfLimitedPartnershipUnitsWithPostTerminationPayOutAmount_019e4774-a73f-77ba-ae62-de22c41fea20" xlink:href="nmrk-20260630.xsd#nmrk_NotionalValueOfLimitedPartnershipUnitsWithPostTerminationPayOutAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7e20-a4c8-34bd9573e57f" xlink:to="loc_nmrk_NotionalValueOfLimitedPartnershipUnitsWithPostTerminationPayOutAmount_019e4774-a73f-77ba-ae62-de22c41fea20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingGrantDateFairValue_019e4774-a73f-7bab-8dd1-4fc96cb26320" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7e20-a4c8-34bd9573e57f" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingGrantDateFairValue_019e4774-a73f-7bab-8dd1-4fc96cb26320" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019e4774-a73f-7936-af52-e42febc8a463" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7e20-a4c8-34bd9573e57f" xlink:to="loc_us-gaap_LimitedPartnersCapitalAccountUnitsOutstanding_019e4774-a73f-7936-af52-e42febc8a463" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e4774-a73f-7342-a51a-87a18cf3c9d2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7e20-a4c8-34bd9573e57f" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_019e4774-a73f-7342-a51a-87a18cf3c9d2" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofCompensationExpenseRelatedtoLimitedPartnershipUnitsthatwereNotRedeemedDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofCompensationExpenseRelatedtoLimitedPartnershipUnitsthatwereNotRedeemedDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofCompensationExpenseRelatedtoLimitedPartnershipUnitsthatwereNotRedeemedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7aa0-9059-158c10ca0a61" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d84-8a15-c72e671c032b" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7aa0-9059-158c10ca0a61" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d84-8a15-c72e671c032b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-7005-8d73-803d6622c41a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d84-8a15-c72e671c032b" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-7005-8d73-803d6622c41a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7005-8d73-803d6622c41a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-7005-8d73-803d6622c41a" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7005-8d73-803d6622c41a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7657-accb-e350689be529" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-7005-8d73-803d6622c41a" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7657-accb-e350689be529" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-7a2b-a122-1aa730c044cf" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7657-accb-e350689be529" xlink:to="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-7a2b-a122-1aa730c044cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7036-9cc7-6b3d64175f63" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d84-8a15-c72e671c032b" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7036-9cc7-6b3d64175f63" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7036-9cc7-6b3d64175f63_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7036-9cc7-6b3d64175f63" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7036-9cc7-6b3d64175f63_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7d16-b3dc-d60e39bd221c" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7036-9cc7-6b3d64175f63" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7d16-b3dc-d60e39bd221c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a73f-750b-85b3-7c709b7eebc1" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7d16-b3dc-d60e39bd221c" xlink:to="loc_srt_ParentCompanyMember_019e4774-a73f-750b-85b3-7c709b7eebc1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019e4774-a73f-7872-bebb-e0a2a3c97b39" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeBenefitsAndShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7aa0-9059-158c10ca0a61" xlink:to="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019e4774-a73f-7872-bebb-e0a2a3c97b39" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofGrantofConversionRightstoNewmarkEmployeesDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofGrantofConversionRightstoNewmarkEmployeesDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofGrantofConversionRightstoNewmarkEmployeesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7877-9bb8-fe383cccb46d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d97-aed2-74a7801c5dd7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7877-9bb8-fe383cccb46d" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d97-aed2-74a7801c5dd7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-711c-8b39-64b859f24284" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7d97-aed2-74a7801c5dd7" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-711c-8b39-64b859f24284" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-711c-8b39-64b859f24284_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-711c-8b39-64b859f24284" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-711c-8b39-64b859f24284_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7fcd-b584-b4fd47a29a08" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountAxis_019e4774-a73f-711c-8b39-64b859f24284" xlink:to="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7fcd-b584-b4fd47a29a08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-7ed7-b0f4-967aeb42fd7b" xlink:href="nmrk-20260630.xsd#nmrk_LimitedPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PartnerTypeOfPartnersCapitalAccountNameDomain_019e4774-a73f-7fcd-b584-b4fd47a29a08" xlink:to="loc_nmrk_LimitedPartnershipUnitsMember_019e4774-a73f-7ed7-b0f4-967aeb42fd7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NotionalValueOfLimitedPartnershipUnitsEligibleForConversion_019e4774-a73f-75d0-9628-b2304e7e05cf" xlink:href="nmrk-20260630.xsd#nmrk_NotionalValueOfLimitedPartnershipUnitsEligibleForConversion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7877-9bb8-fe383cccb46d" xlink:to="loc_nmrk_NotionalValueOfLimitedPartnershipUnitsEligibleForConversion_019e4774-a73f-75d0-9628-b2304e7e05cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingGrantDateFairValue_019e4774-a73f-7562-876b-146e0721a959" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7877-9bb8-fe383cccb46d" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingGrantDateFairValue_019e4774-a73f-7562-876b-146e0721a959" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofActivityAssociatedwithRestrictedStockUnitsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofActivityAssociatedwithRestrictedStockUnitsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofActivityAssociatedwithRestrictedStockUnitsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7193-b949-969a2cc5f624" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-70c8-b71e-4a5a21eef8b7" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7193-b949-969a2cc5f624" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-70c8-b71e-4a5a21eef8b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a73f-71c3-89e7-b26754956a21" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-70c8-b71e-4a5a21eef8b7" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a73f-71c3-89e7-b26754956a21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-71c3-89e7-b26754956a21_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-71c3-89e7-b26754956a21" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-71c3-89e7-b26754956a21_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7863-9630-0e43e94a63f5" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-71c3-89e7-b26754956a21" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7863-9630-0e43e94a63f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-7567-b975-b5cb46cc2888" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7863-9630-0e43e94a63f5" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-7567-b975-b5cb46cc2888" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-720a-a7be-1e0d31df4de4" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-70c8-b71e-4a5a21eef8b7" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-720a-a7be-1e0d31df4de4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-720a-a7be-1e0d31df4de4_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-720a-a7be-1e0d31df4de4" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-720a-a7be-1e0d31df4de4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-77f6-aa46-ab7a9477ba5b" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-720a-a7be-1e0d31df4de4" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-77f6-aa46-ab7a9477ba5b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_NewmarkHoldingsLimitedPartnershipMember_019e4774-a73f-7731-a45e-5e0fb91daa31" xlink:href="nmrk-20260630.xsd#nmrk_NewmarkHoldingsLimitedPartnershipMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-77f6-aa46-ab7a9477ba5b" xlink:to="loc_nmrk_NewmarkHoldingsLimitedPartnershipMember_019e4774-a73f-7731-a45e-5e0fb91daa31" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_BGCHoldingPartnershipUnitsMember_019e4774-a73f-7dd4-90d7-8db2de71d65c" xlink:href="nmrk-20260630.xsd#nmrk_BGCHoldingPartnershipUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-77f6-aa46-ab7a9477ba5b" xlink:to="loc_nmrk_BGCHoldingPartnershipUnitsMember_019e4774-a73f-7dd4-90d7-8db2de71d65c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_019e4774-a73f-7082-8911-409b1b2c4b7d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-70c8-b71e-4a5a21eef8b7" xlink:to="loc_srt_RangeAxis_019e4774-a73f-7082-8911-409b1b2c4b7d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a73f-7082-8911-409b1b2c4b7d_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_019e4774-a73f-7082-8911-409b1b2c4b7d" xlink:to="loc_srt_RangeMember_019e4774-a73f-7082-8911-409b1b2c4b7d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_019e4774-a73f-71cc-bb21-912e03108cc0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_019e4774-a73f-7082-8911-409b1b2c4b7d" xlink:to="loc_srt_RangeMember_019e4774-a73f-71cc-bb21-912e03108cc0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_019e4774-a73f-7285-a338-c118a43ea8a6" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a73f-71cc-bb21-912e03108cc0" xlink:to="loc_srt_MinimumMember_019e4774-a73f-7285-a338-c118a43ea8a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_019e4774-a73f-7559-bd20-17690bd4d63d" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_019e4774-a73f-71cc-bb21-912e03108cc0" xlink:to="loc_srt_MaximumMember_019e4774-a73f-7559-bd20-17690bd4d63d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-7193-b949-969a2cc5f624" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockAwardForfeituresAbstract_019e4774-a73f-7a8e-a0ef-b2c1c0d1629d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockAwardForfeituresAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:to="loc_us-gaap_RestrictedStockAwardForfeituresAbstract_019e4774-a73f-7a8e-a0ef-b2c1c0d1629d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019e4774-a73f-77af-804c-407bf6625991" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedStockAwardForfeituresAbstract_019e4774-a73f-7a8e-a0ef-b2c1c0d1629d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019e4774-a73f-77af-804c-407bf6625991" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_019e4774-a73f-7ed9-bb9f-d94c3f10383e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedStockAwardForfeituresAbstract_019e4774-a73f-7a8e-a0ef-b2c1c0d1629d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_019e4774-a73f-7ed9-bb9f-d94c3f10383e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised_019e4774-a73f-7f2d-85d9-81e6c76ae601" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedStockAwardForfeituresAbstract_019e4774-a73f-7a8e-a0ef-b2c1c0d1629d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercised_019e4774-a73f-7f2d-85d9-81e6c76ae601" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019e4774-a73f-7f23-acef-43efda43a467" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedStockAwardForfeituresAbstract_019e4774-a73f-7a8e-a0ef-b2c1c0d1629d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsForfeitures_019e4774-a73f-7f23-acef-43efda43a467" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_019e4774-a73f-7efc-8287-8ab3b5081575" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_019e4774-a73f-7887-875d-b68adc1c3681" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_019e4774-a73f-7887-875d-b68adc1c3681" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e4774-a73f-715a-9110-07d78c21c697" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_019e4774-a73f-7887-875d-b68adc1c3681" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e4774-a73f-715a-9110-07d78c21c697" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e4774-a73f-734a-be38-ab924aa925c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_019e4774-a73f-7887-875d-b68adc1c3681" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_019e4774-a73f-734a-be38-ab924aa925c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019e4774-a73f-782b-b0ae-6c428896763e" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_019e4774-a73f-7887-875d-b68adc1c3681" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_019e4774-a73f-782b-b0ae-6c428896763e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019e4774-a73f-70cd-991c-7ee595ea857c" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_019e4774-a73f-7887-875d-b68adc1c3681" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_019e4774-a73f-70cd-991c-7ee595ea857c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_019e4774-a73f-735f-be6e-66b6d87ad7f9" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_FairValueAmountRollForward_019e4774-a73f-7abc-a976-01bc1ff5562b" xlink:href="nmrk-20260630.xsd#nmrk_FairValueAmountRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:to="loc_nmrk_FairValueAmountRollForward_019e4774-a73f-7abc-a976-01bc1ff5562b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue_019e4774-a73f-712c-bea1-ed1b7b7afc29" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_FairValueAmountRollForward_019e4774-a73f-7abc-a976-01bc1ff5562b" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue_019e4774-a73f-712c-bea1-ed1b7b7afc29" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedFairValue_019e4774-a73f-70aa-88aa-2bf6c9eb3680" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_FairValueAmountRollForward_019e4774-a73f-7abc-a976-01bc1ff5562b" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantedFairValue_019e4774-a73f-70aa-88aa-2bf6c9eb3680" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledFairValue_019e4774-a73f-74dd-88d7-4f836b5787d1" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_FairValueAmountRollForward_019e4774-a73f-7abc-a976-01bc1ff5562b" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsSettledFairValue_019e4774-a73f-74dd-88d7-4f836b5787d1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedFairValue_019e4774-a73f-7ece-9674-7c4eb292dbc2" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_nmrk_FairValueAmountRollForward_019e4774-a73f-7abc-a976-01bc1ff5562b" xlink:to="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedFairValue_019e4774-a73f-7ece-9674-7c4eb292dbc2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue_019e4774-a73f-78dd-8aaf-0c2294c2cbd9" xlink:href="nmrk-20260630.xsd#nmrk_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedFairValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_019e4774-a73f-73cf-b94b-1906f0a5c422" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:to="loc_srt_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased_019e4774-a73f-73cf-b94b-1906f0a5c422" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019e4774-a73f-76cd-936d-4fd164e38f45" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingRollForward_019e4774-a73f-77b1-8f09-a329bcaa4742" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_019e4774-a73f-76cd-936d-4fd164e38f45" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CompensationScheduleofExpenseRelatedtoNewmarkandBGCRSUsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CompensationScheduleofExpenseRelatedtoNewmarkandBGCRSUsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CompensationScheduleofExpenseRelatedtoNewmarkandBGCRSUsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-731d-9ed2-572640212302" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7eb0-aa5a-2e3abec90664" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-731d-9ed2-572640212302" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7eb0-aa5a-2e3abec90664" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7a66-bef5-54679a5b8bd0" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7eb0-aa5a-2e3abec90664" xlink:to="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7a66-bef5-54679a5b8bd0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7a66-bef5-54679a5b8bd0_default" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7a66-bef5-54679a5b8bd0" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7a66-bef5-54679a5b8bd0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7a34-861e-be83f7af7536" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidatedEntitiesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_019e4774-a73f-7a66-bef5-54679a5b8bd0" xlink:to="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7a34-861e-be83f7af7536" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ParentCompanyMember_019e4774-a73f-79e2-ba98-508e8c6254f7" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ParentCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_019e4774-a73f-7a34-861e-be83f7af7536" xlink:to="loc_srt_ParentCompanyMember_019e4774-a73f-79e2-ba98-508e8c6254f7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_019e4774-a73f-77d1-90dc-67bf834ea290" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_019e4774-a73f-7eb0-aa5a-2e3abec90664" xlink:to="loc_us-gaap_AwardTypeAxis_019e4774-a73f-77d1-90dc-67bf834ea290" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-77d1-90dc-67bf834ea290_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-77d1-90dc-67bf834ea290" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-77d1-90dc-67bf834ea290_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7605-a678-1a7ddd9e88f3" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_019e4774-a73f-77d1-90dc-67bf834ea290" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7605-a678-1a7ddd9e88f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-7c21-9e1a-67eb6a26435d" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_019e4774-a73f-7605-a678-1a7ddd9e88f3" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_019e4774-a73f-7c21-9e1a-67eb6a26435d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019e4774-a73f-7ce6-a026-0f798608a79a" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeBenefitsAndShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_019e4774-a73f-731d-9ed2-572640212302" xlink:to="loc_us-gaap_EmployeeBenefitsAndShareBasedCompensation_019e4774-a73f-7ce6-a026-0f798608a79a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#CommitmentsandContingenciesNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/CommitmentsandContingenciesNarrativeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesLineItems_019e4774-a73f-7575-8114-3c910c008e67" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LossContingenciesTable_019e4774-a73f-73db-96a9-89139522a3c4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e4774-a73f-7575-8114-3c910c008e67" xlink:to="loc_us-gaap_LossContingenciesTable_019e4774-a73f-73db-96a9-89139522a3c4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019e4774-a73f-7190-901f-f3e3dc85b547" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e4774-a73f-73db-96a9-89139522a3c4" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019e4774-a73f-7190-901f-f3e3dc85b547" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019e4774-a73f-7190-901f-f3e3dc85b547_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019e4774-a73f-7190-901f-f3e3dc85b547" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019e4774-a73f-7190-901f-f3e3dc85b547_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019e4774-a73f-7e6e-9775-10a761dc53a0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_019e4774-a73f-7190-901f-f3e3dc85b547" xlink:to="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019e4774-a73f-7e6e-9775-10a761dc53a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionLoansMember_019e4774-a73f-76dd-8f54-eb0889ddebfe" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConstructionLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_019e4774-a73f-7e6e-9775-10a761dc53a0" xlink:to="loc_us-gaap_ConstructionLoansMember_019e4774-a73f-76dd-8f54-eb0889ddebfe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a73f-7c0d-a0fd-64fa7300e365" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LossContingenciesTable_019e4774-a73f-73db-96a9-89139522a3c4" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a73f-7c0d-a0fd-64fa7300e365" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a73f-7c0d-a0fd-64fa7300e365_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a73f-7c0d-a0fd-64fa7300e365" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a73f-7c0d-a0fd-64fa7300e365_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a73f-72af-a697-dbe030737920" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_019e4774-a73f-7c0d-a0fd-64fa7300e365" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a73f-72af-a697-dbe030737920" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_AcquisitionsFromTwoThousandTwentyTwoThroughTwoThousandTwentySixMember_019e4774-a73f-7faa-91c3-ae24a46ad1fb" xlink:href="nmrk-20260630.xsd#nmrk_AcquisitionsFromTwoThousandTwentyTwoThroughTwoThousandTwentySixMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_019e4774-a73f-72af-a697-dbe030737920" xlink:to="loc_nmrk_AcquisitionsFromTwoThousandTwentyTwoThroughTwoThousandTwentySixMember_019e4774-a73f-7faa-91c3-ae24a46ad1fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractualObligation_019e4774-a73f-7b3c-bdbb-8635e835a9c6" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ContractualObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e4774-a73f-7575-8114-3c910c008e67" xlink:to="loc_us-gaap_ContractualObligation_019e4774-a73f-7b3c-bdbb-8635e835a9c6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_019e4774-a73f-7903-9aff-03886a6898ba" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LossContingenciesLineItems_019e4774-a73f-7575-8114-3c910c008e67" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_019e4774-a73f-7903-9aff-03886a6898ba" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.nmrk.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="nmrk-20260630.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.nmrk.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_019e4774-a73f-720b-af38-b021a1e2d996" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_us-gaap_SubsequentEventTable_019e4774-a73f-720b-af38-b021a1e2d996" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_019e4774-a73f-7b3a-915e-3fd8f5647d26" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019e4774-a73f-720b-af38-b021a1e2d996" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_019e4774-a73f-7b3a-915e-3fd8f5647d26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019e4774-a73f-7b3a-915e-3fd8f5647d26_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019e4774-a73f-7b3a-915e-3fd8f5647d26" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019e4774-a73f-7b3a-915e-3fd8f5647d26_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_019e4774-a73f-7cad-8d62-97fb5ae03aed" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_019e4774-a73f-7b3a-915e-3fd8f5647d26" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_019e4774-a73f-7cad-8d62-97fb5ae03aed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_019e4774-a73f-7918-8062-0d420b6f19ef" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_019e4774-a73f-7cad-8d62-97fb5ae03aed" xlink:to="loc_us-gaap_SubsequentEventMember_019e4774-a73f-7918-8062-0d420b6f19ef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_019e4774-a73f-76b9-8cb0-be7f400b4430" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019e4774-a73f-720b-af38-b021a1e2d996" xlink:to="loc_us-gaap_StatementClassOfStockAxis_019e4774-a73f-76b9-8cb0-be7f400b4430" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a73f-76b9-8cb0-be7f400b4430_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a73f-76b9-8cb0-be7f400b4430" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a73f-76b9-8cb0-be7f400b4430_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_019e4774-a73f-74ae-9447-7e316060a0cf" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_019e4774-a73f-76b9-8cb0-be7f400b4430" xlink:to="loc_us-gaap_ClassOfStockDomain_019e4774-a73f-74ae-9447-7e316060a0cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassAMember_019e4774-a73f-7411-a3e6-25959a820ad1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a73f-74ae-9447-7e316060a0cf" xlink:to="loc_us-gaap_CommonClassAMember_019e4774-a73f-7411-a3e6-25959a820ad1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonClassBMember_019e4774-a73f-7cef-bef9-274672e43da0" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonClassBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_019e4774-a73f-74ae-9447-7e316060a0cf" xlink:to="loc_us-gaap_CommonClassBMember_019e4774-a73f-7cef-bef9-274672e43da0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fcad7-ac0d-7d6a-859a-e03df4248ed4" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_019e4774-a73f-720b-af38-b021a1e2d996" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fcad7-ac0d-7d6a-859a-e03df4248ed4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fcad7-ac0d-7d6a-859a-e03df4248ed4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fcad7-ac0d-7d6a-859a-e03df4248ed4" xlink:to="loc_us-gaap_RelatedPartyDomain_019fcad7-ac0d-7d6a-859a-e03df4248ed4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RelatedPartyDomain_019fcad7-ac0d-7eba-8c25-36dde41dcf86" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_019fcad7-ac0d-7d6a-859a-e03df4248ed4" xlink:to="loc_us-gaap_RelatedPartyDomain_019fcad7-ac0d-7eba-8c25-36dde41dcf86" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ChiefExecutiveOfficerMember_019fcad7-ac0d-77e1-8fab-1ce89f0d3658" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ChiefExecutiveOfficerMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_019fcad7-ac0d-7eba-8c25-36dde41dcf86" xlink:to="loc_srt_ChiefExecutiveOfficerMember_019fcad7-ac0d-77e1-8fab-1ce89f0d3658" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensation_019fdcbc-2612-72c8-922c-8ae7f1d70106" xlink:href="nmrk-20260630.xsd#nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensation_019fdcbc-2612-72c8-922c-8ae7f1d70106" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensationBaseSalary_019fdcbc-2612-7460-b258-16b73fa9c72c" xlink:href="nmrk-20260630.xsd#nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensationBaseSalary"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensationBaseSalary_019fdcbc-2612-7460-b258-16b73fa9c72c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensationCashAwardGranted_019fdcbc-2612-76c7-b79f-a89772f3f7cc" xlink:href="nmrk-20260630.xsd#nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensationCashAwardGranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_nmrk_CompensationArrangementWithIndividualAggregateAnnualCompensationCashAwardGranted_019fdcbc-2612-76c7-b79f-a89772f3f7cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_nmrk_PartnershipInterestInInvestmentPercentage_019fdcbc-2612-7fcf-a610-e0957d918b0c" xlink:href="nmrk-20260630.xsd#nmrk_PartnershipInterestInInvestmentPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_nmrk_PartnershipInterestInInvestmentPercentage_019fdcbc-2612-7fcf-a610-e0957d918b0c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_019fcad7-ac0d-7da2-86a0-ce335c2b33e1" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_019fcad7-ac0d-7da2-86a0-ce335c2b33e1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_019e4774-a73f-7230-9641-340c0ac282e2" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_019e4774-a73f-7cda-acfa-15db9b119605" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_019e4774-a73f-7230-9641-340c0ac282e2" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/srt/role/srt-eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-roles-2026.xsd#eedm1"/>
  <link:definitionLink xlink:role="http://fasb.org/srt/role/srt-eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_AccountsPayableAndOtherAccruedLiabilitiesCurrent" xlink:type="arc" order="41"/>
  </link:definitionLink>
</link:linkbase>
