<?xml version="1.0" encoding="utf-8"?>
<!--XBRL document created with Toppan Merrill Bridge  11.4.0.1 -->
<!--Based on XBRL 2.1-->
<!--Created on: 8/13/2026 12:05:05 AM-->
<!--Modified on: 8/13/2026 12:05:05 AM-->
<link:linkbase xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" 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" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrli="http://www.xbrl.org/2003/instance">
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#StatementCondensedBalanceSheetsParenthetical" roleURI="http://www.eyenoviabio.com/role/StatementCondensedBalanceSheetsParenthetical" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#StatementCondensedStatementsOfChangesInStockholdersEquityDeficit" roleURI="http://www.eyenoviabio.com/role/StatementCondensedStatementsOfChangesInStockholdersEquityDeficit" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#StatementCondensedStatementsOfChangesInStockholdersEquityDeficitParenthetical" roleURI="http://www.eyenoviabio.com/role/StatementCondensedStatementsOfChangesInStockholdersEquityDeficitParenthetical" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#StatementCondensedStatementsOfCashFlows" roleURI="http://www.eyenoviabio.com/role/StatementCondensedStatementsOfCashFlows" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureBusinessOrganizationNatureOfOperationsAndBasisOfPresentationDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureBusinessOrganizationNatureOfOperationsAndBasisOfPresentationDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureManagementSLiquidityPlansDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureManagementSLiquidityPlansDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesCashAndCashEquivalentsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCashAndCashEquivalentsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesHyperlendPrivatePoolParticipationAgreementAndRevenueSharingAgreementDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesHyperlendPrivatePoolParticipationAgreementAndRevenueSharingAgreementDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesHyperlendPrivatePoolParticipationAgreementAndRevenueSharingAgreementDefaultDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesHyperlendPrivatePoolParticipationAgreementAndRevenueSharingAgreementDefaultDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesOtcHypeOptionsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesOtcHypeOptionsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesFairValueMeasurementDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesFairValueMeasurementDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSummaryOfSignificantAccountingPoliciesAssetsHeldForSaleDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesAssetsHeldForSaleDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureNetIncomeLossPerShareOfCommonStockDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureNetIncomeLossPerShareOfCommonStockDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureNetIncomeLossPerShareOfCommonStockCalculationOfWeightedAverageDilutiveSharesOfCommonStockDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureNetIncomeLossPerShareOfCommonStockCalculationOfWeightedAverageDilutiveSharesOfCommonStockDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsNativeStakingAndTemporaryHypeAssetUseServiceAgreementsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsNativeStakingAndTemporaryHypeAssetUseServiceAgreementsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsDigitalAssetsReceivableDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalAssetsReceivableDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsOtcHypeOptionsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsOtcHypeOptionsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsHyperionRyskVaultSharesDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsHyperionRyskVaultSharesDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsDigitalAssetReconciliationDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalAssetReconciliationDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsDigitalAssetsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalAssetsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureDigitalAssetsDigitalIntangibleAssetsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalIntangibleAssetsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureNotesPayableDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureNotesPayableDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureNotesPayableAvenueLoanMaturitiesDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureNotesPayableAvenueLoanMaturitiesDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureNotesPayableFirstInsuranceFundingLoanDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureNotesPayableFirstInsuranceFundingLoanDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureCommitmentsAndContingenciesHausAgreementsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureCommitmentsAndContingenciesHausAgreementsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureCommitmentsAndContingenciesHyperlendRevenueSharingAgreementDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureCommitmentsAndContingenciesHyperlendRevenueSharingAgreementDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureCommitmentsAndContingenciesJointValidatorOperatorSAgreementDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureCommitmentsAndContingenciesJointValidatorOperatorSAgreementDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitCommonStockIssuancesDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitCommonStockIssuancesDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitAtMarketProgramDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitAtMarketProgramDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitSeriesPreferredStockSecuritiesPurchaseAgreementsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitSeriesPreferredStockSecuritiesPurchaseAgreementsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitStockBasedCompensationExpenseDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitStockBasedCompensationExpenseDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitStockBasedCompensationExpenseDefaultDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitStockBasedCompensationExpenseDefaultDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitWarrantsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitWarrantsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureStockholdersEquityDeficitAdditionalInformationDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitAdditionalInformationDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSegmentReportingSignificantExpensesDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSegmentReportingSignificantExpensesDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSegmentReportingSegmentAssetsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSegmentReportingSegmentAssetsDetails" />
  <link:roleRef xlink:type="simple" xlink:href="hypd-20260630.xsd#DisclosureSubsequentEventsDetails" roleURI="http://www.eyenoviabio.com/role/DisclosureSubsequentEventsDetails" />
  <link:roleRef roleURI="http://fasb.org/srt/role/srt-eedm/ExtensibleEnumerationLists" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-roles-2026.xsd#eedm1" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://www.esma.europa.eu/xbrl/esef/arcrole/wider-narrower" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/arcrole/esma-arcrole-2018-11-21.xsd#wider-narrower" />
  <link:roleRef roleURI="http://www.eyenoviabio.com/role/DisclosureStandardAndCustomAxisDomainDefaults" xlink:href="hypd-20260630.xsd#DisclosureStandardAndCustomAxisDomainDefaults" xlink:type="simple" />
  <link:roleRef xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-roles-2026.xsd#eedm" roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" />
  <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/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: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:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended" xlink:title="Extensible Enumeration Domain Members" />
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStandardAndCustomAxisDomainDefaults" xlink:type="extended" xlink:title="99900 - Disclosure - Standard And Custom Axis Domain Defaults">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis_1" xlink:title="us-gaap_StatementClassOfStockAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain_1" xlink:title="us-gaap_ClassOfStockDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_StatementClassOfStockAxis_1" xlink:to="us-gaap_ClassOfStockDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_StatementClassOfStockAxis_1 To us-gaap_ClassOfStockDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis_1" xlink:title="us-gaap_StatementEquityComponentsAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain_1" xlink:title="us-gaap_EquityComponentDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_StatementEquityComponentsAxis_1" xlink:to="us-gaap_EquityComponentDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_StatementEquityComponentsAxis_1 To us-gaap_EquityComponentDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_1" xlink:title="us-gaap_SubsidiarySaleOfStockAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_1" xlink:title="us-gaap_SaleOfStockNameOfTransactionDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_SubsidiarySaleOfStockAxis_1" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_SubsidiarySaleOfStockAxis_1 To us-gaap_SaleOfStockNameOfTransactionDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis_1" xlink:title="us-gaap_SubsequentEventTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain_1" xlink:title="us-gaap_SubsequentEventTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_SubsequentEventTypeAxis_1" xlink:to="us-gaap_SubsequentEventTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_SubsequentEventTypeAxis_1 To us-gaap_SubsequentEventTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OptionIndexedToIssuersEquityTypeAxis" xlink:label="us-gaap_OptionIndexedToIssuersEquityTypeAxis_1" xlink:title="us-gaap_OptionIndexedToIssuersEquityTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OptionIndexedToIssuersEquityTypeDomain" xlink:label="us-gaap_OptionIndexedToIssuersEquityTypeDomain_1" xlink:title="us-gaap_OptionIndexedToIssuersEquityTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_OptionIndexedToIssuersEquityTypeAxis_1" xlink:to="us-gaap_OptionIndexedToIssuersEquityTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_OptionIndexedToIssuersEquityTypeAxis_1 To us-gaap_OptionIndexedToIssuersEquityTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis_1" xlink:title="us-gaap_AwardTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1" xlink:title="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_AwardTypeAxis_1" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_AwardTypeAxis_1 To us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis_1" xlink:title="srt_RangeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RangeMember" xlink:label="srt_RangeMember_1" xlink:title="srt_RangeMember_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_RangeAxis_1" xlink:to="srt_RangeMember_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_RangeAxis_1 To srt_RangeMember_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis_1" xlink:title="us-gaap_TypeOfArrangementAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_1" xlink:title="us-gaap_ArrangementsAndNonarrangementTransactionsMember_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_TypeOfArrangementAxis_1" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_TypeOfArrangementAxis_1 To us-gaap_ArrangementsAndNonarrangementTransactionsMember_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="us-gaap_RelatedPartyTransactionAxis_1" xlink:title="us-gaap_RelatedPartyTransactionAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="us-gaap_RelatedPartyTransactionDomain_1" xlink:title="us-gaap_RelatedPartyTransactionDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_RelatedPartyTransactionAxis_1" xlink:to="us-gaap_RelatedPartyTransactionDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_RelatedPartyTransactionAxis_1 To us-gaap_RelatedPartyTransactionDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_1" xlink:title="us-gaap_PropertyPlantAndEquipmentByTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_1" xlink:title="us-gaap_PropertyPlantAndEquipmentTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis_1" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_PropertyPlantAndEquipmentByTypeAxis_1 To us-gaap_PropertyPlantAndEquipmentTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="us-gaap_FairValueByAssetClassAxis_1" xlink:title="us-gaap_FairValueByAssetClassAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1" xlink:title="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_FairValueByAssetClassAxis_1" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_FairValueByAssetClassAxis_1 To us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis_1" xlink:title="us-gaap_DebtInstrumentAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain_1" xlink:title="us-gaap_DebtInstrumentNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_DebtInstrumentAxis_1" xlink:to="us-gaap_DebtInstrumentNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_DebtInstrumentAxis_1 To us-gaap_DebtInstrumentNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermDebtTypeAxis" xlink:label="us-gaap_ShortTermDebtTypeAxis_1" xlink:title="us-gaap_ShortTermDebtTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShortTermDebtTypeDomain" xlink:label="us-gaap_ShortTermDebtTypeDomain_1" xlink:title="us-gaap_ShortTermDebtTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_ShortTermDebtTypeAxis_1" xlink:to="us-gaap_ShortTermDebtTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_ShortTermDebtTypeAxis_1 To us-gaap_ShortTermDebtTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PeriodAxis" xlink:label="hypd_PeriodAxis_1" xlink:title="eyen_PeriodAxis_1" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PeriodTypeDomain" xlink:label="hypd_PeriodTypeDomain_1" xlink:title="eyen_PeriodTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="hypd_PeriodAxis_1" xlink:to="hypd_PeriodTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:eyen_PeriodAxis_1 To eyen_PeriodTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis_1" xlink:title="us-gaap_FinancialInstrumentAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1" xlink:title="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_FinancialInstrumentAxis_1" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_FinancialInstrumentAxis_1 To us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis_1" xlink:title="us-gaap_IncomeTaxAuthorityAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain_1" xlink:title="us-gaap_IncomeTaxAuthorityDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_IncomeTaxAuthorityAxis_1" xlink:to="us-gaap_IncomeTaxAuthorityDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_IncomeTaxAuthorityAxis_1 To us-gaap_IncomeTaxAuthorityDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementScenarioAxis" xlink:label="srt_StatementScenarioAxis_1" xlink:title="srt_StatementScenarioAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="srt_ScenarioUnspecifiedDomain_1" xlink:title="srt_ScenarioUnspecifiedDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_StatementScenarioAxis_1" xlink:to="srt_ScenarioUnspecifiedDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_StatementScenarioAxis_1 To srt_ScenarioUnspecifiedDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis_1" xlink:title="srt_StatementGeographicalAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain_1" xlink:title="srt_SegmentGeographicalDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_StatementGeographicalAxis_1" xlink:to="srt_SegmentGeographicalDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_StatementGeographicalAxis_1 To srt_SegmentGeographicalDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_1" xlink:title="us-gaap_DerivativeInstrumentRiskAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain_1" xlink:title="us-gaap_DerivativeContractTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_DerivativeInstrumentRiskAxis_1" xlink:to="us-gaap_DerivativeContractTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_DerivativeInstrumentRiskAxis_1 To us-gaap_DerivativeContractTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_1" xlink:title="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_1" xlink:title="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_1" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_1 To us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_1" xlink:title="us-gaap_ClassOfWarrantOrRightAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_1" xlink:title="us-gaap_ClassOfWarrantOrRightDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_ClassOfWarrantOrRightAxis_1" xlink:to="us-gaap_ClassOfWarrantOrRightDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_ClassOfWarrantOrRightAxis_1 To us-gaap_ClassOfWarrantOrRightDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis_1" xlink:title="us-gaap_PlanNameAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain_1" xlink:title="us-gaap_PlanNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_PlanNameAxis_1" xlink:to="us-gaap_PlanNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_PlanNameAxis_1 To us-gaap_PlanNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1" xlink:title="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain_1" xlink:title="us-gaap_RelatedPartyDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1" xlink:to="us-gaap_RelatedPartyDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1 To us-gaap_RelatedPartyDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingAxis" xlink:label="us-gaap_VestingAxis_1" xlink:title="us-gaap_VestingAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VestingDomain" xlink:label="us-gaap_VestingDomain_1" xlink:title="us-gaap_VestingDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_VestingAxis_1" xlink:to="us-gaap_VestingDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_VestingAxis_1 To us-gaap_VestingDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_TitleOfIndividualAxis" xlink:label="srt_TitleOfIndividualAxis_1" xlink:title="srt_TitleOfIndividualAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain_1" xlink:title="srt_TitleOfIndividualWithRelationshipToEntityDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_TitleOfIndividualAxis_1" xlink:to="srt_TitleOfIndividualWithRelationshipToEntityDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_TitleOfIndividualAxis_1 To srt_TitleOfIndividualWithRelationshipToEntityDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="us-gaap_RetirementPlanTypeAxis_1" xlink:title="us-gaap_RetirementPlanTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="us-gaap_RetirementPlanTypeDomain_1" xlink:title="us-gaap_RetirementPlanTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_RetirementPlanTypeAxis_1" xlink:to="us-gaap_RetirementPlanTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_RetirementPlanTypeAxis_1 To us-gaap_RetirementPlanTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipAxis" xlink:label="srt_OwnershipAxis_1" xlink:title="srt_OwnershipAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_OwnershipDomain" xlink:label="srt_OwnershipDomain_1" xlink:title="srt_OwnershipDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_OwnershipAxis_1" xlink:to="srt_OwnershipDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_OwnershipAxis_1 To srt_OwnershipDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="us-gaap_LineOfCreditFacilityAxis_1" xlink:title="us-gaap_LineOfCreditFacilityAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="us-gaap_LineOfCreditFacilityLenderDomain_1" xlink:title="us-gaap_LineOfCreditFacilityLenderDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_LineOfCreditFacilityAxis_1" xlink:to="us-gaap_LineOfCreditFacilityLenderDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_LineOfCreditFacilityAxis_1 To us-gaap_LineOfCreditFacilityLenderDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis_1" xlink:title="us-gaap_VariableRateAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain_1" xlink:title="us-gaap_VariableRateDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_VariableRateAxis_1" xlink:to="us-gaap_VariableRateDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_VariableRateAxis_1 To us-gaap_VariableRateDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis_1" xlink:title="srt_CounterpartyNameAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_1" xlink:title="srt_RepurchaseAgreementCounterpartyNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_CounterpartyNameAxis_1" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_CounterpartyNameAxis_1 To srt_RepurchaseAgreementCounterpartyNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_1" xlink:title="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember_1" xlink:title="us-gaap_TypeOfAdoptionMember_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_1" xlink:to="us-gaap_TypeOfAdoptionMember_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_1 To us-gaap_TypeOfAdoptionMember_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis_1" xlink:title="srt_CumulativeEffectPeriodOfAdoptionAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain_1" xlink:title="srt_CumulativeEffectPeriodOfAdoptionDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAxis_1" xlink:to="srt_CumulativeEffectPeriodOfAdoptionDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_CumulativeEffectPeriodOfAdoptionAxis_1 To srt_CumulativeEffectPeriodOfAdoptionDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1" xlink:title="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_1" xlink:title="us-gaap_AntidilutiveSecuritiesNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1" xlink:to="us-gaap_AntidilutiveSecuritiesNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1 To us-gaap_AntidilutiveSecuritiesNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="us-gaap_LongtermDebtTypeAxis_1" xlink:title="us-gaap_LongtermDebtTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="us-gaap_LongtermDebtTypeDomain_1" xlink:title="us-gaap_LongtermDebtTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_LongtermDebtTypeAxis_1" xlink:to="us-gaap_LongtermDebtTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_LongtermDebtTypeAxis_1 To us-gaap_LongtermDebtTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_1" xlink:title="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1" xlink:title="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_1" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_1 To us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesByNatureOfContingencyAxis" xlink:label="us-gaap_LossContingenciesByNatureOfContingencyAxis_1" xlink:title="us-gaap_LossContingenciesByNatureOfContingencyAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingencyNatureDomain" xlink:label="us-gaap_LossContingencyNatureDomain_1" xlink:title="us-gaap_LossContingencyNatureDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_LossContingenciesByNatureOfContingencyAxis_1" xlink:to="us-gaap_LossContingencyNatureDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_LossContingenciesByNatureOfContingencyAxis_1 To us-gaap_LossContingencyNatureDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="us-gaap_MeasurementInputTypeAxis_1" xlink:title="us-gaap_MeasurementInputTypeAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain_1" xlink:title="us-gaap_MeasurementInputTypeDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_MeasurementInputTypeAxis_1" xlink:to="us-gaap_MeasurementInputTypeDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_MeasurementInputTypeAxis_1 To us-gaap_MeasurementInputTypeDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="us-gaap_StatementBusinessSegmentsAxis_1" xlink:title="us-gaap_StatementBusinessSegmentsAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain_1" xlink:title="us-gaap_SegmentDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_StatementBusinessSegmentsAxis_1" xlink:to="us-gaap_SegmentDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_StatementBusinessSegmentsAxis_1 To us-gaap_SegmentDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis" xlink:label="srt_ConsolidationItemsAxis_1" xlink:title="srt_ConsolidationItemsAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain" xlink:label="srt_ConsolidationItemsDomain_1" xlink:title="srt_ConsolidationItemsDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_ConsolidationItemsAxis_1" xlink:to="srt_ConsolidationItemsDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_ConsolidationItemsAxis_1 To srt_ConsolidationItemsDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_1" xlink:title="us-gaap_FairValueByMeasurementFrequencyAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_1" xlink:title="us-gaap_FairValueMeasurementFrequencyDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis_1" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_FairValueByMeasurementFrequencyAxis_1 To us-gaap_FairValueMeasurementFrequencyDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="us-gaap_FairValueByMeasurementBasisAxis_1" xlink:title="us-gaap_FairValueByMeasurementBasisAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="us-gaap_PortionAtFairValueFairValueDisclosureMember_1" xlink:title="us-gaap_PortionAtFairValueFairValueDisclosureMember_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_FairValueByMeasurementBasisAxis_1" xlink:to="us-gaap_PortionAtFairValueFairValueDisclosureMember_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_FairValueByMeasurementBasisAxis_1 To us-gaap_PortionAtFairValueFairValueDisclosureMember_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_1" xlink:title="us-gaap_FairValueByFairValueHierarchyLevelAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1" xlink:title="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis_1" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_FairValueByFairValueHierarchyLevelAxis_1 To us-gaap_FairValueMeasurementsFairValueHierarchyDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis_1" xlink:title="srt_CryptoAssetAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain_1" xlink:title="srt_CryptoAssetDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="srt_CryptoAssetAxis_1" xlink:to="srt_CryptoAssetDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:srt_CryptoAssetAxis_1 To srt_CryptoAssetDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis" xlink:label="us-gaap_CashAndCashEquivalentsAxis_1" xlink:title="us-gaap_CashAndCashEquivalentsAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1" xlink:title="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_CashAndCashEquivalentsAxis_1" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_CashAndCashEquivalentsAxis_1 To us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="us-gaap_DisposalGroupClassificationAxis_1" xlink:title="us-gaap_DisposalGroupClassificationAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="us-gaap_DisposalGroupClassificationDomain_1" xlink:title="us-gaap_DisposalGroupClassificationDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_DisposalGroupClassificationAxis_1" xlink:to="us-gaap_DisposalGroupClassificationDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_DisposalGroupClassificationAxis_1 To us-gaap_DisposalGroupClassificationDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1" xlink:title="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1" xlink:title="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1" xlink:to="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_1 To us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_1" order="1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusAxis" xlink:label="us-gaap_PledgedStatusAxis_1" xlink:title="us-gaap_PledgedStatusAxis_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusDomain" xlink:label="us-gaap_PledgedStatusDomain_1" xlink:title="us-gaap_PledgedStatusDomain_1" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_PledgedStatusAxis_1" xlink:to="us-gaap_PledgedStatusDomain_1" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:title="definition:us-gaap_PledgedStatusAxis_1 To us-gaap_PledgedStatusDomain_1" order="1" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://fasb.org/srt/role/srt-eedm/ExtensibleEnumerationLists" xlink:type="extended" xlink:title="SRT Extensible Enumeration Domain Members">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract_1" xlink:title="us-gaap_IncomeStatementAbstract_1" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetImpairmentCharges" xlink:label="us-gaap_AssetImpairmentCharges" xlink:title="us-gaap_AssetImpairmentCharges" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_IncomeStatementAbstract_1" xlink:to="us-gaap_AssetImpairmentCharges" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:title="definition:us-gaap_IncomeStatementAbstract To us-gaap_AssetImpairmentCharges_3" order="1" priority="0" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssetImpairmentCharges" xlink:label="us-gaap_OtherAssetImpairmentCharges" xlink:title="us-gaap_OtherAssetImpairmentCharges" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_IncomeStatementAbstract_1" xlink:to="us-gaap_OtherAssetImpairmentCharges" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:title="definition:us-gaap_IncomeStatementAbstract To us-gaap_OtherAssetImpairmentCharges_3" order="2" priority="0" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_OtherAssetImpairmentLoss" xlink:label="hypd_OtherAssetImpairmentLoss_2" xlink:title="hypd_OtherAssetImpairmentLoss_2" />
    <link:definitionArc xlink:type="arc" xlink:from="us-gaap_IncomeStatementAbstract_1" xlink:to="hypd_OtherAssetImpairmentLoss_2" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:title="definition:us-gaap_IncomeStatementAbstract To hypd_OtherAssetImpairmentLoss_3" order="3" priority="0" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/StatementCondensedBalanceSheetsParenthetical" xlink:type="extended" xlink:title="995200105 - Statement - Condensed Balance Sheets (Parenthetical)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementClassOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesAuthorized" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesIssued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesOutstanding" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockLiquidationPreferenceValue" xlink:label="us-gaap_PreferredStockLiquidationPreferenceValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockLiquidationPreferenceValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesAuthorized" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesIssued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesOutstanding" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonShares" xlink:label="us-gaap_TreasuryStockCommonShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockCommonShares" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/StatementCondensedStatementsOfChangesInStockholdersEquityDeficit" xlink:type="extended" xlink:title="995200300 - Statement - Condensed Statements of Changes in Stockholders' Equity (Deficit)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_CommonStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockMember" xlink:label="us-gaap_PreferredStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_PreferredStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonMember" xlink:label="us-gaap_TreasuryStockCommonMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_TreasuryStockCommonMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PublicOfferingMember" xlink:label="hypd_PublicOfferingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_PublicOfferingMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AtMarketOfferingMember" xlink:label="hypd_AtMarketOfferingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_AtMarketOfferingMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrivatePlacementMember" xlink:label="us-gaap_PrivatePlacementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_PrivatePlacementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquity" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesOutstanding" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockCommonShares" xlink:label="us-gaap_TreasuryStockCommonShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockCommonShares" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueStockDividend" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockDividend" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueStockDividend" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockDividendsShares" xlink:label="us-gaap_CommonStockDividendsShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockDividendsShares" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockIssuedDuringPeriodValueWarrantsExercised" xlink:label="hypd_StockIssuedDuringPeriodValueWarrantsExercised" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_StockIssuedDuringPeriodValueWarrantsExercised" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockIssuedDuringPeriodSharesWarrantsExercised" xlink:label="hypd_StockIssuedDuringPeriodSharesWarrantsExercised" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_StockIssuedDuringPeriodSharesWarrantsExercised" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_RestrictedStockIssuedDuringPeriodValueNewIssues" xlink:label="hypd_RestrictedStockIssuedDuringPeriodValueNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_RestrictedStockIssuedDuringPeriodValueNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_RestrictedStockIssuedDuringPeriodSharesNewIssues" xlink:label="hypd_RestrictedStockIssuedDuringPeriodSharesNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_RestrictedStockIssuedDuringPeriodSharesNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="13" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation" xlink:label="us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="14" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockIssuedDuringPeriodValueConversionOfPreferredStock" xlink:label="hypd_StockIssuedDuringPeriodValueConversionOfPreferredStock" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="15" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_StockIssuedDuringPeriodValueConversionOfPreferredStock" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockIssuedDuringPeriodSharesConversionOfPreferredStock" xlink:label="hypd_StockIssuedDuringPeriodSharesConversionOfPreferredStock" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="16" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_StockIssuedDuringPeriodSharesConversionOfPreferredStock" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" xlink:label="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="17" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockRepurchasedAndRetiredDuringPeriodValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockRepurchasedAndRetiredDuringPeriodShares" xlink:label="us-gaap_StockRepurchasedAndRetiredDuringPeriodShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="18" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockRepurchasedAndRetiredDuringPeriodShares" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionAbstract" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="19" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionAbstract" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionAbstract" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationRestrictedStockUnitsRequisiteServicePeriodRecognition" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockIssuedDuringPeriodValueInducedExerciseOfWarrants" xlink:label="hypd_StockIssuedDuringPeriodValueInducedExerciseOfWarrants" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="20" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_StockIssuedDuringPeriodValueInducedExerciseOfWarrants" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockIssuedDuringPeriodSharesInducedExerciseOfWarrants" xlink:label="hypd_StockIssuedDuringPeriodSharesInducedExerciseOfWarrants" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="21" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_StockIssuedDuringPeriodSharesInducedExerciseOfWarrants" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockSplit" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockSplit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="22" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockSplit" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" xlink:label="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="23" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesReverseStockSplits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="24" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalWarrantIssued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="25" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueIssuedForServices" xlink:label="us-gaap_StockIssuedDuringPeriodValueIssuedForServices" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="26" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueIssuedForServices" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" xlink:label="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="27" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="28" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalDividendsInExcessOfRetainedEarnings" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="29" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="30" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="31" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="32" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetIncomeLoss" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/StatementCondensedStatementsOfChangesInStockholdersEquityDeficitParenthetical" xlink:type="extended" xlink:title="995200305 - Statement - Condensed Statements of Changes in Stockholders' Equity (Deficit) (Parenthetical)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AtMarketOfferingMember" xlink:label="hypd_AtMarketOfferingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_AtMarketOfferingMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PublicOfferingMember" xlink:label="hypd_PublicOfferingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_PublicOfferingMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrivatePlacementMember" xlink:label="us-gaap_PrivatePlacementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_PrivatePlacementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockDividendRatePerDollarAmount" xlink:label="us-gaap_PreferredStockDividendRatePerDollarAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockDividendRatePerDollarAmount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ProceedsOfStockIssuedDuringPeriodGross" xlink:label="hypd_ProceedsOfStockIssuedDuringPeriodGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_StatementLineItems" xlink:to="hypd_ProceedsOfStockIssuedDuringPeriodGross" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PaymentsOfStockIssuanceCosts" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/StatementCondensedStatementsOfCashFlows" xlink:type="extended" xlink:title="995200400 - Statement - Condensed Statements of Cash Flows">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AtMarketOfferingMember" xlink:label="hypd_AtMarketOfferingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_AtMarketOfferingMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PublicOfferingMember" xlink:label="hypd_PublicOfferingMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_PublicOfferingMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PrivatePlacementMember" xlink:label="us-gaap_PrivatePlacementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_PrivatePlacementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetIncomeLoss" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensation" xlink:label="us-gaap_ShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ShareBasedCompensation" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_FairValueAdjustmentOfSharesIssuedForDividend" xlink:label="hypd_FairValueAdjustmentOfSharesIssuedForDividend" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_FairValueAdjustmentOfSharesIssuedForDividend" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AmortizationOfDebtDiscount" xlink:label="hypd_AmortizationOfDebtDiscount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_AmortizationOfDebtDiscount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NonCashLeaseExpense" xlink:label="hypd_NonCashLeaseExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_NonCashLeaseExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" xlink:label="hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_GainLossOnExtinguishmentOfLiability" xlink:label="hypd_GainLossOnExtinguishmentOfLiability" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_GainLossOnExtinguishmentOfLiability" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedGainLossOperating" xlink:label="us-gaap_CryptoAssetRealizedGainLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_CryptoAssetRealizedGainLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetUnrealizedGainLossOperating" xlink:label="us-gaap_CryptoAssetUnrealizedGainLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_CryptoAssetUnrealizedGainLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax" xlink:label="us-gaap_GainLossOnDerivativeInstrumentsNetPretax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_GainLossOnDerivativeInstrumentsNetPretax" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" xlink:label="us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NoncashRevenuesNet" xlink:label="hypd_NoncashRevenuesNet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_NoncashRevenuesNet" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NoncashInterestIncomeFromDigitalAssetsReceivables" xlink:label="hypd_NoncashInterestIncomeFromDigitalAssetsReceivables" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_NoncashInterestIncomeFromDigitalAssetsReceivables" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NonCashPortionOfOtherIncome" xlink:label="hypd_NonCashPortionOfOtherIncome" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="13" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="hypd_NonCashPortionOfOtherIncome" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaidInKindInterest" xlink:label="us-gaap_PaidInKindInterest" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="14" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_PaidInKindInterest" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="15" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IncreaseDecreaseInDepositAsset" xlink:label="hypd_IncreaseDecreaseInDepositAsset" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="hypd_IncreaseDecreaseInDepositAsset" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOtherAccountsPayableAndAccruedLiabilities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncreaseDecreaseInOperatingLeaseLiability" xlink:label="us-gaap_IncreaseDecreaseInOperatingLeaseLiability" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingLeaseLiability" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentForAcquisitionCryptoAsset" xlink:label="us-gaap_PaymentForAcquisitionCryptoAsset" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_PaymentForAcquisitionCryptoAsset" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromDisposalCryptoAsset" xlink:label="us-gaap_ProceedsFromDisposalCryptoAsset" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromDisposalCryptoAsset" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PaymentsToAcquireFinancialInstrument" xlink:label="hypd_PaymentsToAcquireFinancialInstrument" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="hypd_PaymentsToAcquireFinancialInstrument" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ProceedsFromSaleOfFinancialInstrument" xlink:label="hypd_ProceedsFromSaleOfFinancialInstrument" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="hypd_ProceedsFromSaleOfFinancialInstrument" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ProceedsOfStockIssuedDuringPeriodGross" xlink:label="hypd_ProceedsOfStockIssuedDuringPeriodGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="hypd_ProceedsOfStockIssuedDuringPeriodGross" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ProceedsFromIssuanceOfPreferredStockAndWarrantsPrivatePlacement" xlink:label="hypd_ProceedsFromIssuanceOfPreferredStockAndWarrantsPrivatePlacement" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="hypd_ProceedsFromIssuanceOfPreferredStockAndWarrantsPrivatePlacement" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ProceedsFromInducedExerciseOfWarrants" xlink:label="hypd_ProceedsFromInducedExerciseOfWarrants" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="hypd_ProceedsFromInducedExerciseOfWarrants" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromWarrantExercises" xlink:label="us-gaap_ProceedsFromWarrantExercises" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromWarrantExercises" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsOfStockIssuanceCosts" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RepaymentsOfNotesPayable" xlink:label="us-gaap_RepaymentsOfNotesPayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_RepaymentsOfNotesPayable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfDebtRestructuringCosts" xlink:label="us-gaap_PaymentsOfDebtRestructuringCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsOfDebtRestructuringCosts" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PaymentsOfCostsOnInducedExerciseOfWarrants" xlink:label="hypd_PaymentsOfCostsOnInducedExerciseOfWarrants" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="hypd_PaymentsOfCostsOnInducedExerciseOfWarrants" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ReverseStockSplitSettlementOfFractionalShares" xlink:label="hypd_ReverseStockSplitSettlementOfFractionalShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="hypd_ReverseStockSplitSettlementOfFractionalShares" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestPaidCapitalized" xlink:label="us-gaap_InterestPaidCapitalized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_InterestPaidCapitalized" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:label="us-gaap_NoncashInvestingAndFinancingItemsAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NoncashInvestingAndFinancingItemsAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ExtinguishmentOfDebtAmount" xlink:label="us-gaap_ExtinguishmentOfDebtAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="us-gaap_ExtinguishmentOfDebtAmount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ModificationOfDebtFairValueAtModificationDate" xlink:label="hypd_ModificationOfDebtFairValueAtModificationDate" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_ModificationOfDebtFairValueAtModificationDate" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExchangeOfDigitalIntangibleAssetsForDigitalIntangibleAssetsReceivable" xlink:label="hypd_ExchangeOfDigitalIntangibleAssetsForDigitalIntangibleAssetsReceivable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_ExchangeOfDigitalIntangibleAssetsForDigitalIntangibleAssetsReceivable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExchangeOfDigitalIntangibleAssetsReceivableForDigitalIntangibleAssets" xlink:label="hypd_ExchangeOfDigitalIntangibleAssetsReceivableForDigitalIntangibleAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_ExchangeOfDigitalIntangibleAssetsReceivableForDigitalIntangibleAssets" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsReceivedForDigitalAssetsReceivable" xlink:label="hypd_DigitalAssetsReceivedForDigitalAssetsReceivable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_DigitalAssetsReceivedForDigitalAssetsReceivable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DepositOfDigitalAssetsIntoDigitalInvestmentAccount" xlink:label="hypd_DepositOfDigitalAssetsIntoDigitalInvestmentAccount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_DepositOfDigitalAssetsIntoDigitalInvestmentAccount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_RedemptionOfDigitalAssetsFromDigitalInvestmentAccount" xlink:label="hypd_RedemptionOfDigitalAssetsFromDigitalInvestmentAccount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_RedemptionOfDigitalAssetsFromDigitalInvestmentAccount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_WarrantModificationAndAdditionalWarrantsIncrementalValue" xlink:label="hypd_WarrantModificationAndAdditionalWarrantsIncrementalValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_WarrantModificationAndAdditionalWarrantsIncrementalValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PurchaseOfInsurancePremiumFinancedByShortTermNotePayable" xlink:label="hypd_PurchaseOfInsurancePremiumFinancedByShortTermNotePayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_PurchaseOfInsurancePremiumFinancedByShortTermNotePayable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_SharesIssuedForAccruedDividends" xlink:label="hypd_SharesIssuedForAccruedDividends" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_SharesIssuedForAccruedDividends" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PreferredStockAccruedDividends" xlink:label="hypd_PreferredStockAccruedDividends" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_PreferredStockAccruedDividends" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_SharesWithheldForEmployeeTaxLiabilities" xlink:label="hypd_SharesWithheldForEmployeeTaxLiabilities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_SharesWithheldForEmployeeTaxLiabilities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_TreasurySharesRetired" xlink:label="hypd_TreasurySharesRetired" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="13" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_TreasurySharesRetired" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DepositOfDigitalAssetsIntoLiquidStakingActivities" xlink:label="hypd_DepositOfDigitalAssetsIntoLiquidStakingActivities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="14" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_DepositOfDigitalAssetsIntoLiquidStakingActivities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LiabilityForDigitalAssetsReceivedUnderPartnershipAgreement" xlink:label="hypd_LiabilityForDigitalAssetsReceivedUnderPartnershipAgreement" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="15" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_LiabilityForDigitalAssetsReceivedUnderPartnershipAgreement" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConversionOfStockAmountIssued1" xlink:label="us-gaap_ConversionOfStockAmountIssued1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="16" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="us-gaap_ConversionOfStockAmountIssued1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IssuanceOfCommonStockRelatedToVestedRestrictedStockUnits" xlink:label="hypd_IssuanceOfCommonStockRelatedToVestedRestrictedStockUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="17" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_IssuanceOfCommonStockRelatedToVestedRestrictedStockUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsAcquiredInExchangeForFinancialInstrument" xlink:label="hypd_DigitalAssetsAcquiredInExchangeForFinancialInstrument" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="18" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_DigitalAssetsAcquiredInExchangeForFinancialInstrument" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsDisposedInExchangeForFinancialInstrument" xlink:label="hypd_DigitalAssetsDisposedInExchangeForFinancialInstrument" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="19" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_DigitalAssetsDisposedInExchangeForFinancialInstrument" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ConversionOfOneFinancialInstrumentToAnother" xlink:label="hypd_ConversionOfOneFinancialInstrumentToAnother" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="20" xlink:from="us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:to="hypd_ConversionOfOneFinancialInstrumentToAnother" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureBusinessOrganizationNatureOfOperationsAndBasisOfPresentationDetails" xlink:type="extended" xlink:title="99940101 - Disclosure - Business Organization, Nature of Operations and Basis of Presentation (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NatureOfOperationsBasisOfPresentationAndLiquidityTable" xlink:label="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityTable" xlink:to="us-gaap_SubsequentEventTypeAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="us-gaap_DisposalGroupClassificationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityTable" xlink:to="us-gaap_DisposalGroupClassificationAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="us-gaap_DisposalGroupClassificationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DisposalGroupClassificationAxis" xlink:to="us-gaap_DisposalGroupClassificationDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" xlink:label="us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DisposalGroupClassificationDomain" xlink:to="us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NatureOfOperationsBasisOfPresentationAndLiquidityLineitems" xlink:label="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityLineitems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityLineitems" xlink:to="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentDecreaseForgiveness" xlink:label="us-gaap_DebtInstrumentDecreaseForgiveness" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityLineitems" xlink:to="us-gaap_DebtInstrumentDecreaseForgiveness" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" xlink:label="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityLineitems" xlink:to="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation" xlink:label="us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_NatureOfOperationsBasisOfPresentationAndLiquidityLineitems" xlink:to="us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureManagementSLiquidityPlansDetails" xlink:type="extended" xlink:title="99940201 - Disclosure - Management's Liquidity Plans (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LiquidityPlanTable" xlink:label="hypd_LiquidityPlanTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_LiquidityPlanTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeLiquidStakedTokensMember" xlink:label="hypd_HypeLiquidStakedTokensMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeLiquidStakedTokensMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="hypd_LiquidityPlanTable" xlink:to="srt_CounterpartyNameAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KinetiqResearchPteAndPierTwoPtyLtdMember" xlink:label="hypd_KinetiqResearchPteAndPierTwoPtyLtdMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="hypd_KinetiqResearchPteAndPierTwoPtyLtdMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="hypd_LiquidityPlanTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_May2026PublicEquityIssuanceMember" xlink:label="hypd_May2026PublicEquityIssuanceMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_May2026PublicEquityIssuanceMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LiquidityPlanLineItems" xlink:label="hypd_LiquidityPlanLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="hypd_LiquidityPlanTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_WorkingCapitalDeficit" xlink:label="hypd_WorkingCapitalDeficit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="hypd_WorkingCapitalDeficit" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_NetIncomeLoss" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:label="us-gaap_SaleOfStockConsiderationReceivedOnTransaction" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_SaleOfStockConsiderationReceivedOnTransaction" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_CommonStockSharesIssued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValueNoncurrent" xlink:label="us-gaap_CryptoAssetFairValueNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="us-gaap_CryptoAssetFairValueNoncurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetUnstakingQuePeriod" xlink:label="hypd_CryptoAssetUnstakingQuePeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="hypd_CryptoAssetUnstakingQuePeriod" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetTemporaryUseAgreementThresholdNoticePeriodForNonRenewal" xlink:label="hypd_CryptoAssetTemporaryUseAgreementThresholdNoticePeriodForNonRenewal" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="hypd_LiquidityPlanLineItems" xlink:to="hypd_CryptoAssetTemporaryUseAgreementThresholdNoticePeriodForNonRenewal" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCashAndCashEquivalentsDetails" xlink:type="extended" xlink:title="99940301 - Disclosure - Summary of Significant Accounting Policies - Cash and Cash Equivalents (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureTable" xlink:label="hypd_AccountingPoliciesDisclosureTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAxis" xlink:label="us-gaap_CashAndCashEquivalentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_CashAndCashEquivalentsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_CashAndCashEquivalentsAxis" xlink:to="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="us-gaap_USTreasurySecuritiesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:to="us-gaap_USTreasurySecuritiesMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureLineItems" xlink:label="hypd_AccountingPoliciesDisclosureLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="hypd_AccountingPoliciesDisclosureTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesHyperlendPrivatePoolParticipationAgreementAndRevenueSharingAgreementDetails" xlink:type="extended" xlink:title="99940302 - Disclosure - Summary of Significant Accounting Policies - HyperLend Private Pool Participation Agreement and Revenue-Sharing Agreement (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_TypeOfArrangementAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PartnershipAgreementMember" xlink:label="hypd_PartnershipAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_PartnershipAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PrivatePoolParticipationAgreementMember" xlink:label="hypd_PrivatePoolParticipationAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_PrivatePoolParticipationAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_RevenueSharingAgreementMember" xlink:label="hypd_RevenueSharingAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_RevenueSharingAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PrivatePoolParticipationAgreementAndRevenueSharingAgreementMember" xlink:label="hypd_PrivatePoolParticipationAgreementAndRevenueSharingAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_PrivatePoolParticipationAgreementAndRevenueSharingAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HyperlendTokensMember" xlink:label="hypd_HyperlendTokensMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HyperlendTokensMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsReceived" xlink:label="hypd_CryptoAssetNumberOfUnitsReceived" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsReceived" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NumberOfPartnershipAgreements" xlink:label="hypd_NumberOfPartnershipAgreements" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_NumberOfPartnershipAgreements" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesHyperlendPrivatePoolParticipationAgreementAndRevenueSharingAgreementDefaultDetails" xlink:type="extended" xlink:title="40302 - Disclosure - Summary of Significant Accounting Policies - HyperLend Private Pool Participation Agreement and Revenue-Sharing Agreement Default (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_TypeOfArrangementAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PartnershipAgreementMember" xlink:label="hypd_PartnershipAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_PartnershipAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PrivatePoolParticipationAgreementMember" xlink:label="hypd_PrivatePoolParticipationAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_PrivatePoolParticipationAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_RevenueSharingAgreementMember" xlink:label="hypd_RevenueSharingAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_RevenueSharingAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PrivatePoolParticipationAgreementAndRevenueSharingAgreementMember" xlink:label="hypd_PrivatePoolParticipationAgreementAndRevenueSharingAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_PrivatePoolParticipationAgreementAndRevenueSharingAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HyperlendTokensMember" xlink:label="hypd_HyperlendTokensMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HyperlendTokensMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsReceived" xlink:label="hypd_CryptoAssetNumberOfUnitsReceived" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsReceived" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NumberOfPartnershipAgreements" xlink:label="hypd_NumberOfPartnershipAgreements" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_NumberOfPartnershipAgreements" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesOtcHypeOptionsDetails" xlink:type="extended" xlink:title="99940303 - Disclosure - Summary of Significant Accounting Policies - OTC HYPE Options (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureTable" xlink:label="hypd_AccountingPoliciesDisclosureTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureLineItems" xlink:label="hypd_AccountingPoliciesDisclosureLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="hypd_AccountingPoliciesDisclosureTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilitiesCurrent" xlink:label="us-gaap_DerivativeLiabilitiesCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="us-gaap_DerivativeLiabilitiesCurrent" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesFairValueMeasurementDetails" xlink:type="extended" xlink:title="99940304 - Disclosure - Summary of Significant Accounting Policies - Fair Value Measurement (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureTable" xlink:label="hypd_AccountingPoliciesDisclosureTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_FairValueByMeasurementFrequencyAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_FairValueByMeasurementFrequencyAxis" xlink:to="us-gaap_FairValueMeasurementFrequencyDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="us-gaap_FairValueMeasurementsRecurringMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_FairValueMeasurementFrequencyDomain" xlink:to="us-gaap_FairValueMeasurementsRecurringMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="us-gaap_FairValueByMeasurementBasisAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_FairValueByMeasurementBasisAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="us-gaap_PortionAtFairValueFairValueDisclosureMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_FairValueByMeasurementBasisAxis" xlink:to="us-gaap_PortionAtFairValueFairValueDisclosureMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember" xlink:label="us-gaap_CarryingReportedAmountFairValueDisclosureMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:to="us-gaap_CarryingReportedAmountFairValueDisclosureMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="us-gaap_EstimateOfFairValueFairValueDisclosureMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:to="us-gaap_EstimateOfFairValueFairValueDisclosureMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="us-gaap_FairValueInputsLevel1Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel1Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="4" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KntqDigitalAssetsMember" xlink:label="hypd_KntqDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_KntqDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureLineItems" xlink:label="hypd_AccountingPoliciesDisclosureLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="hypd_AccountingPoliciesDisclosureTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValueNoncurrent" xlink:label="us-gaap_CryptoAssetFairValueNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="us-gaap_CryptoAssetFairValueNoncurrent" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSummaryOfSignificantAccountingPoliciesAssetsHeldForSaleDetails" xlink:type="extended" xlink:title="99940305 - Disclosure - Summary of Significant Accounting Policies - Assets Held For Sale (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureTable" xlink:label="hypd_AccountingPoliciesDisclosureTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationAxis" xlink:label="us-gaap_DisposalGroupClassificationAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_DisposalGroupClassificationAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupClassificationDomain" xlink:label="us-gaap_DisposalGroupClassificationDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DisposalGroupClassificationAxis" xlink:to="us-gaap_DisposalGroupClassificationDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" xlink:label="us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DisposalGroupClassificationDomain" xlink:to="us-gaap_DisposalGroupHeldforsaleNotDiscontinuedOperationsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:to="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_BiotechOperationsMember" xlink:label="hypd_BiotechOperationsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:to="hypd_BiotechOperationsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="hypd_AccountingPoliciesDisclosureTable" xlink:to="us-gaap_SubsequentEventTypeAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AccountingPoliciesDisclosureLineItems" xlink:label="hypd_AccountingPoliciesDisclosureLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="hypd_AccountingPoliciesDisclosureTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation" xlink:label="us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseImpairmentLoss" xlink:label="us-gaap_OperatingLeaseImpairmentLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="us-gaap_OperatingLeaseImpairmentLoss" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentDecreaseForgiveness" xlink:label="us-gaap_DebtInstrumentDecreaseForgiveness" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="us-gaap_DebtInstrumentDecreaseForgiveness" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LicenseTerminationSettlementPayment" xlink:label="hypd_LicenseTerminationSettlementPayment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="hypd_LicenseTerminationSettlementPayment" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LicenseTerminationCostReimbursement" xlink:label="hypd_LicenseTerminationCostReimbursement" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="hypd_AccountingPoliciesDisclosureLineItems" xlink:to="hypd_LicenseTerminationCostReimbursement" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureNetIncomeLossPerShareOfCommonStockDetails" xlink:type="extended" xlink:title="99940401 - Disclosure - Net Income (Loss) Per Share of Common Stock (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="us-gaap_StatementClassOfStockAxis" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DilutiveSecurities" xlink:label="us-gaap_DilutiveSecurities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_DilutiveSecurities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:to="us-gaap_NetIncomeLoss" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockDividendsIncomeStatementImpact" xlink:label="us-gaap_PreferredStockDividendsIncomeStatementImpact" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:to="us-gaap_PreferredStockDividendsIncomeStatementImpact" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic" xlink:label="us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:to="us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesBasic" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:to="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasic" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted" xlink:label="us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:to="us-gaap_UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted" xlink:label="us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:to="us-gaap_NetIncomeLossAvailableToCommonStockholdersDiluted" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesIssuedBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesIssuedBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesIssuedBasic" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesRestrictedStock" xlink:label="us-gaap_WeightedAverageNumberOfSharesRestrictedStock" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesRestrictedStock" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:label="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:to="us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IncrementalCommonSharesAttributableToDilutiveEffectOfRestrictedStockUnits" xlink:label="hypd_IncrementalCommonSharesAttributableToDilutiveEffectOfRestrictedStockUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:to="hypd_IncrementalCommonSharesAttributableToDilutiveEffectOfRestrictedStockUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustmentAbstract" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_EarningsPerShareBasic" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:to="us-gaap_EarningsPerShareDiluted" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureNetIncomeLossPerShareOfCommonStockCalculationOfWeightedAverageDilutiveSharesOfCommonStockDetails" xlink:type="extended" xlink:title="99940402 - Disclosure - Net Income (Loss) Per Share of Common Stock - Calculation of Weighted Average Dilutive Shares of Common Stock (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:to="us-gaap_AntidilutiveSecuritiesNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_EmployeeStockOptionMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantMember" xlink:label="us-gaap_WarrantMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_WarrantMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="us-gaap_RestrictedStockUnitsRSUMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="us-gaap_RestrictedStockUnitsRSUMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_SeriesaConvertiblePreferredStockMember" xlink:label="hypd_SeriesaConvertiblePreferredStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_AntidilutiveSecuritiesNameDomain" xlink:to="hypd_SeriesaConvertiblePreferredStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsNativeStakingAndTemporaryHypeAssetUseServiceAgreementsDetails" xlink:type="extended" xlink:title="99940601 - Disclosure - Digital Assets - Native Staking and Temporary HYPE Asset Use Service Agreements (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_TypeOfArrangementAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeAssetUseServiceAgreementMember" xlink:label="hypd_HypeAssetUseServiceAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_HypeAssetUseServiceAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_UsDollarPeggedStablecoinMember" xlink:label="hypd_UsDollarPeggedStablecoinMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_UsDollarPeggedStablecoinMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsStaked" xlink:label="hypd_CryptoAssetNumberOfUnitsStaked" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsStaked" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetNumberOfUnits" xlink:label="us-gaap_CryptoAssetNumberOfUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetNumberOfUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsRewardEarned" xlink:label="hypd_CryptoAssetNumberOfUnitsRewardEarned" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsRewardEarned" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IndefiniteLivedIntangibleAssetsNumberOfUnitsRedeemedOrSold" xlink:label="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnitsRedeemedOrSold" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnitsRedeemedOrSold" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalAssetsReceivableDetails" xlink:type="extended" xlink:title="99940602 - Disclosure - Digital Assets - Digital Assets Receivable (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsReceivableMember" xlink:label="hypd_DigitalAssetsReceivableMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_DigitalAssetsReceivableMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalIntangibleAssetsReceivableMember" xlink:label="hypd_DigitalIntangibleAssetsReceivableMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_DigitalIntangibleAssetsReceivableMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_DerivativeInstrumentRiskAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CallOptionMember" xlink:label="us-gaap_CallOptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_CallOptionMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestIncomeOperating" xlink:label="us-gaap_InterestIncomeOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_InterestIncomeOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableAllowanceForCreditLossNonCurrent" xlink:label="hypd_CryptoAssetsReceivableAllowanceForCreditLossNonCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetsReceivableAllowanceForCreditLossNonCurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableAllowanceForCreditLossReversal" xlink:label="hypd_CryptoAssetsReceivableAllowanceForCreditLossReversal" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetsReceivableAllowanceForCreditLossReversal" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" xlink:label="hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeNumberOfInstrumentsHeld" xlink:label="us-gaap_DerivativeNumberOfInstrumentsHeld" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_DerivativeNumberOfInstrumentsHeld" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableAfterUnamortizedNonrefundableUpfrontFeeAndAllowanceForCreditLossNonCurrent" xlink:label="hypd_CryptoAssetsReceivableAfterUnamortizedNonrefundableUpfrontFeeAndAllowanceForCreditLossNonCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetsReceivableAfterUnamortizedNonrefundableUpfrontFeeAndAllowanceForCreditLossNonCurrent" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsOtcHypeOptionsDetails" xlink:type="extended" xlink:title="99940603 - Disclosure - Digital Assets - OTC HYPE Options (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_DerivativeInstrumentRiskAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PutOptionMember" xlink:label="us-gaap_PutOptionMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_PutOptionMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DerivativeLiabilitiesCurrent" xlink:label="us-gaap_DerivativeLiabilitiesCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_DerivativeLiabilitiesCurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax" xlink:label="us-gaap_GainLossOnDerivativeInstrumentsNetPretax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_GainLossOnDerivativeInstrumentsNetPretax" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsHyperionRyskVaultSharesDetails" xlink:type="extended" xlink:title="99940604 - Disclosure - Digital Assets - Hyperion Rysk Vault Shares (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_UsDollarPeggedStablecoinNativeToHyperliquidEcosystemMember" xlink:label="hypd_UsDollarPeggedStablecoinNativeToHyperliquidEcosystemMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_UsDollarPeggedStablecoinNativeToHyperliquidEcosystemMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HyperionRyskVaultSharesMember" xlink:label="hypd_HyperionRyskVaultSharesMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_HyperionRyskVaultSharesMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetDeposited" xlink:label="hypd_CryptoAssetDeposited" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetDeposited" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsReceived" xlink:label="hypd_CryptoAssetNumberOfUnitsReceived" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsReceived" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetValueOfUnitsReceived" xlink:label="hypd_CryptoAssetValueOfUnitsReceived" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetValueOfUnitsReceived" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsRealizedGainLossOnExchange" xlink:label="hypd_CryptoAssetsRealizedGainLossOnExchange" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetsRealizedGainLossOnExchange" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalAssetReconciliationDetails" xlink:type="extended" xlink:title="99940605 - Disclosure - Digital Assets - Digital Asset Reconciliation (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetActivityTable" xlink:label="us-gaap_CryptoAssetActivityTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetActivityTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsMember" xlink:label="hypd_DigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_DigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsReceivableMember" xlink:label="hypd_DigitalAssetsReceivableMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_DigitalAssetsReceivableMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalIntangibleAssetsMember" xlink:label="hypd_DigitalIntangibleAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_DigitalIntangibleAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalIntangibleAssetsReceivableMember" xlink:label="hypd_DigitalIntangibleAssetsReceivableMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_DigitalIntangibleAssetsReceivableMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetActivityTable" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_UsDollarPeggedStablecoinNativeToHyperliquidEcosystemMember" xlink:label="hypd_UsDollarPeggedStablecoinNativeToHyperliquidEcosystemMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_UsDollarPeggedStablecoinNativeToHyperliquidEcosystemMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetActivityLineItems" xlink:label="us-gaap_CryptoAssetActivityLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_CryptoAssetActivityTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRollForward" xlink:label="us-gaap_CryptoAssetRollForward" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_CryptoAssetRollForward" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsFairValue" xlink:label="hypd_CryptoAssetsFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetsFairValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetReceiptFromPartnershipAgreement" xlink:label="hypd_CryptoAssetReceiptFromPartnershipAgreement" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetReceiptFromPartnershipAgreement" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetPurchase" xlink:label="us-gaap_CryptoAssetPurchase" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="us-gaap_CryptoAssetPurchase" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetDisposition" xlink:label="us-gaap_CryptoAssetDisposition" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="us-gaap_CryptoAssetDisposition" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetDeposited" xlink:label="hypd_CryptoAssetDeposited" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetDeposited" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetRedemption" xlink:label="hypd_CryptoAssetRedemption" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetRedemption" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetDispositions" xlink:label="hypd_CryptoAssetDispositions" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetDispositions" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNetAmountReceivedFromNativeStakingActivities" xlink:label="hypd_CryptoAssetNetAmountReceivedFromNativeStakingActivities" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetNetAmountReceivedFromNativeStakingActivities" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetExchangeOfDigitalIntangibleAssetsForDigitalIntangibleAssetsReceivable" xlink:label="hypd_CryptoAssetExchangeOfDigitalIntangibleAssetsForDigitalIntangibleAssetsReceivable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetExchangeOfDigitalIntangibleAssetsForDigitalIntangibleAssetsReceivable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetExchangeOfDigitalIntangibleAssetsReceivableForDigitalIntangibleAssets" xlink:label="hypd_CryptoAssetExchangeOfDigitalIntangibleAssetsReceivableForDigitalIntangibleAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetExchangeOfDigitalIntangibleAssetsReceivableForDigitalIntangibleAssets" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetSettlementOfDigitalAssetsReceivable" xlink:label="hypd_CryptoAssetSettlementOfDigitalAssetsReceivable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetSettlementOfDigitalAssetsReceivable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsNonCashInterestIncome" xlink:label="hypd_CryptoAssetsNonCashInterestIncome" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetsNonCashInterestIncome" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedAndUnrealizedGainOperating" xlink:label="us-gaap_CryptoAssetRealizedAndUnrealizedGainOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="13" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="us-gaap_CryptoAssetRealizedAndUnrealizedGainOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedAndUnrealizedLossOperating" xlink:label="us-gaap_CryptoAssetRealizedAndUnrealizedLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="14" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="us-gaap_CryptoAssetRealizedAndUnrealizedLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetImpairment" xlink:label="hypd_CryptoAssetImpairment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="15" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetImpairment" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableProvisionForCreditLoss" xlink:label="hypd_CryptoAssetsReceivableProvisionForCreditLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="16" xlink:from="us-gaap_CryptoAssetRollForward" xlink:to="hypd_CryptoAssetsReceivableProvisionForCreditLoss" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsRevenueReceivable" xlink:label="hypd_CryptoAssetsRevenueReceivable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="hypd_CryptoAssetsRevenueReceivable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsCostsAccrued" xlink:label="hypd_CryptoAssetsCostsAccrued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="hypd_CryptoAssetsCostsAccrued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="us-gaap_OtherNonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_OtherNonoperatingIncomeExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetCommissionExpense" xlink:label="hypd_CryptoAssetCommissionExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="hypd_CryptoAssetCommissionExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedGainOperating" xlink:label="us-gaap_CryptoAssetRealizedGainOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_CryptoAssetRealizedGainOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetUnrealizedGainOperating" xlink:label="us-gaap_CryptoAssetUnrealizedGainOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_CryptoAssetUnrealizedGainOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetRealizedLossOperating" xlink:label="us-gaap_CryptoAssetRealizedLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_CryptoAssetRealizedLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetUnrealizedLossOperating" xlink:label="us-gaap_CryptoAssetUnrealizedLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_CryptoAssetActivityLineItems" xlink:to="us-gaap_CryptoAssetUnrealizedLossOperating" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalAssetsDetails" xlink:type="extended" xlink:title="99940606 - Disclosure - Digital Assets - Digital Assets (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetNumberOfUnits" xlink:label="us-gaap_CryptoAssetNumberOfUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetNumberOfUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetCost" xlink:label="us-gaap_CryptoAssetCost" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetCost" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValueNoncurrent" xlink:label="us-gaap_CryptoAssetFairValueNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetFairValueNoncurrent" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureDigitalAssetsDigitalIntangibleAssetsDetails" xlink:type="extended" xlink:title="99940607 - Disclosure - Digital Assets - Digital Intangible Assets (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable" xlink:label="us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LiquidStakingTokenMember" xlink:label="hypd_LiquidStakingTokenMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_LiquidStakingTokenMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KhypeLiquidStakingTokenMember" xlink:label="hypd_KhypeLiquidStakingTokenMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_KhypeLiquidStakingTokenMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KmhypeLiquidStakingTokenMember" xlink:label="hypd_KmhypeLiquidStakingTokenMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_KmhypeLiquidStakingTokenMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KntqLiquidStakingTokenMember" xlink:label="hypd_KntqLiquidStakingTokenMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_KntqLiquidStakingTokenMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HplLiquidStakingTokenMember" xlink:label="hypd_HplLiquidStakingTokenMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_HplLiquidStakingTokenMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_OtherDigitalAssetsMember" xlink:label="hypd_OtherDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_OtherDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" xlink:to="us-gaap_ScheduleOfIndefiniteLivedIntangibleAssetsTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IndefiniteLivedIntangibleAssetsNumberOfUnits" xlink:label="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" xlink:to="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IndefiniteLivedIntangibleAssetsExcludingGoodwillGross" xlink:label="hypd_IndefiniteLivedIntangibleAssetsExcludingGoodwillGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" xlink:to="hypd_IndefiniteLivedIntangibleAssetsExcludingGoodwillGross" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" xlink:label="us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassLineItems" xlink:to="us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureNotesPayableDetails" xlink:type="extended" xlink:title="99940801 - Disclosure - Notes Payable (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ScheduleOfNotesPayableTable" xlink:label="hypd_ScheduleOfNotesPayableTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_ScheduleOfNotesPayableTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_FirstInsuranceFundingLoanMember" xlink:label="hypd_FirstInsuranceFundingLoanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="hypd_FirstInsuranceFundingLoanMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AvenueNotePayableMember" xlink:label="hypd_AvenueNotePayableMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="hypd_AvenueNotePayableMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LoanAndSecurityAgreementWithAvenueVentureOpportunitiesFundL.p.AndAvenueVentureOpportunitiesFundL.p.IiMember" xlink:label="hypd_LoanAndSecurityAgreementWithAvenueVentureOpportunitiesFundL.p.AndAvenueVentureOpportunitiesFundL.p.IiMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="hypd_LoanAndSecurityAgreementWithAvenueVentureOpportunitiesFundL.p.AndAvenueVentureOpportunitiesFundL.p.IiMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableLineItems" xlink:label="hypd_NotesPayableLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_ScheduleOfNotesPayableTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayableCurrentAbstract" xlink:label="us-gaap_NotesPayableCurrentAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_NotesPayableCurrentAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableCurrentGross" xlink:label="hypd_NotesPayableCurrentGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="hypd_NotesPayableCurrentGross" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableNonCurrentGross" xlink:label="hypd_NotesPayableNonCurrentGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="hypd_NotesPayableNonCurrentGross" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableGross" xlink:label="hypd_NotesPayableGross" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="hypd_NotesPayableGross" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscountCurrent" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountCurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscountCurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscountNoncurrent" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscountNoncurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentUnamortizedDiscount" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableCurrentNetOfDebtDiscountCurrentCurrentPortion" xlink:label="hypd_NotesPayableCurrentNetOfDebtDiscountCurrentCurrentPortion" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="hypd_NotesPayableCurrentNetOfDebtDiscountCurrentCurrentPortion" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermNotesPayable" xlink:label="us-gaap_LongTermNotesPayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="us-gaap_LongTermNotesPayable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NotesPayable" xlink:label="us-gaap_NotesPayable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_NotesPayableCurrentAbstract" xlink:to="us-gaap_NotesPayable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PercentageOfDebtInstrumentInterestRateExcludingAmortizationOfDebtDiscount" xlink:label="hypd_PercentageOfDebtInstrumentInterestRateExcludingAmortizationOfDebtDiscount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_PercentageOfDebtInstrumentInterestRateExcludingAmortizationOfDebtDiscount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PaidInKindInterestAccrued" xlink:label="hypd_PaidInKindInterestAccrued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_PaidInKindInterestAccrued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PaidInKindInterestAccruedThroughMaturity" xlink:label="hypd_PaidInKindInterestAccruedThroughMaturity" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_PaidInKindInterestAccruedThroughMaturity" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseNonoperating" xlink:label="us-gaap_InterestExpenseNonoperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_InterestExpenseNonoperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_InterestExpenseDebt" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureNotesPayableAvenueLoanMaturitiesDetails" xlink:type="extended" xlink:title="99940802 - Disclosure - Notes Payable - Avenue Loan maturities (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ScheduleOfNotesPayableTable" xlink:label="hypd_ScheduleOfNotesPayableTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_ScheduleOfNotesPayableTable" xlink:to="us-gaap_DebtInstrumentAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_LoanAndSecurityAgreementWithAvenueVentureOpportunitiesFundL.p.AndAvenueVentureOpportunitiesFundL.p.IiMember" xlink:label="hypd_LoanAndSecurityAgreementWithAvenueVentureOpportunitiesFundL.p.AndAvenueVentureOpportunitiesFundL.p.IiMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="hypd_LoanAndSecurityAgreementWithAvenueVentureOpportunitiesFundL.p.AndAvenueVentureOpportunitiesFundL.p.IiMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableLineItems" xlink:label="hypd_NotesPayableLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_ScheduleOfNotesPayableTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_LongTermDebt" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureNotesPayableFirstInsuranceFundingLoanDetails" xlink:type="extended" xlink:title="99940803 - Disclosure - Notes Payable - FIRST Insurance Funding Loan (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ScheduleOfNotesPayableTable" xlink:label="hypd_ScheduleOfNotesPayableTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_ScheduleOfNotesPayableTable" xlink:to="us-gaap_DebtInstrumentAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_FirstInsuranceFundingLoanMember" xlink:label="hypd_FirstInsuranceFundingLoanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="hypd_FirstInsuranceFundingLoanMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_NotesPayableLineItems" xlink:label="hypd_NotesPayableLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_ScheduleOfNotesPayableTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DebtInstrumentPeriodicPaymentNumberOfInstallments" xlink:label="hypd_DebtInstrumentPeriodicPaymentNumberOfInstallments" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_NotesPayableLineItems" xlink:to="hypd_DebtInstrumentPeriodicPaymentNumberOfInstallments" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentPeriodicPayment" xlink:label="us-gaap_DebtInstrumentPeriodicPayment" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_DebtInstrumentPeriodicPayment" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestExpenseDebtExcludingAmortization" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="hypd_NotesPayableLineItems" xlink:to="us-gaap_InterestExpenseDebtExcludingAmortization" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureCommitmentsAndContingenciesHausAgreementsDetails" xlink:type="extended" xlink:title="99940901 - Disclosure - Commitments and Contingencies - HAUS Agreements (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_LossContingenciesTable" xlink:to="srt_CounterpartyNameAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_SilhouetteGMember" xlink:label="hypd_SilhouetteGMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="hypd_SilhouetteGMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_SubsequentEventTypeAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="us-gaap_LossContingenciesTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="4" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_TypeOfArrangementAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeAssetUseServiceAgreementMember" xlink:label="hypd_HypeAssetUseServiceAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_HypeAssetUseServiceAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_LossContingenciesTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsLinkedToTradingWallet" xlink:label="hypd_CryptoAssetNumberOfUnitsLinkedToTradingWallet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsLinkedToTradingWallet" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_MarketRevenuesPercentage" xlink:label="hypd_MarketRevenuesPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_MarketRevenuesPercentage" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValueNoncurrent" xlink:label="us-gaap_CryptoAssetFairValueNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_CryptoAssetFairValueNoncurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementInitialTerm" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementInitialTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementInitialTerm" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementAutomaticRenewable" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementAutomaticRenewable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementAutomaticRenewable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementTerminatedNotice" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementTerminatedNotice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementTerminatedNotice" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementThresholdPriorWrittenNoticePeriodForTermination" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementThresholdPriorWrittenNoticePeriodForTermination" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementThresholdPriorWrittenNoticePeriodForTermination" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureCommitmentsAndContingenciesHyperlendRevenueSharingAgreementDetails" xlink:type="extended" xlink:title="99940902 - Disclosure - Commitments and Contingencies - HyperLend Revenue-Sharing Agreement (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingTable" xlink:label="us-gaap_CryptoAssetHoldingTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="us-gaap_TypeOfArrangementAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_RevenueSharingAgreementMember" xlink:label="hypd_RevenueSharingAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_RevenueSharingAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_CryptoAssetHoldingTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HyperlendTokensMember" xlink:label="hypd_HyperlendTokensMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HyperlendTokensMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetHoldingLineItems" xlink:label="us-gaap_CryptoAssetHoldingLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="us-gaap_CryptoAssetHoldingTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetSaleRestrictionTerm" xlink:label="hypd_CryptoAssetSaleRestrictionTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetSaleRestrictionTerm" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsToBeStaked" xlink:label="hypd_CryptoAssetNumberOfUnitsToBeStaked" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsToBeStaked" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetThresholdTermForStaking" xlink:label="hypd_CryptoAssetThresholdTermForStaking" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetThresholdTermForStaking" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfNativeUnitsStaked" xlink:label="hypd_CryptoAssetNumberOfNativeUnitsStaked" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetNumberOfNativeUnitsStaked" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetDispositions" xlink:label="hypd_CryptoAssetDispositions" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetDispositions" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetLiquidStakingActivityVestingPeriod" xlink:label="hypd_CryptoAssetLiquidStakingActivityVestingPeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetLiquidStakingActivityVestingPeriod" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetRestrictedNumberOfUnitsFreeTransferable" xlink:label="hypd_CryptoAssetRestrictedNumberOfUnitsFreeTransferable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetRestrictedNumberOfUnitsFreeTransferable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetStakingAndVestingConditionsPenaltyPercentage" xlink:label="hypd_CryptoAssetStakingAndVestingConditionsPenaltyPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_CryptoAssetHoldingLineItems" xlink:to="hypd_CryptoAssetStakingAndVestingConditionsPenaltyPercentage" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureCommitmentsAndContingenciesJointValidatorOperatorSAgreementDetails" xlink:type="extended" xlink:title="99940903 - Disclosure - Commitments and Contingencies - Joint Validator Operator's Agreement (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_LossContingenciesTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_LossContingenciesTable" xlink:to="srt_CounterpartyNameAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KinetiqResearchPteLtdAndMavanServicesPtyLtdMember" xlink:label="hypd_KinetiqResearchPteLtdAndMavanServicesPtyLtdMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="hypd_KinetiqResearchPteLtdAndMavanServicesPtyLtdMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_LossContingenciesTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsInitiatedForStake" xlink:label="hypd_CryptoAssetNumberOfUnitsInitiatedForStake" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsInitiatedForStake" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValueNoncurrent" xlink:label="us-gaap_CryptoAssetFairValueNoncurrent" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_CryptoAssetFairValueNoncurrent" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetJointValidatorAgreementInitialTerm" xlink:label="hypd_CryptoAssetJointValidatorAgreementInitialTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetJointValidatorAgreementInitialTerm" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetJointValidatorAgreementThresholdPriorNoticePeriod" xlink:label="hypd_CryptoAssetJointValidatorAgreementThresholdPriorNoticePeriod" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="hypd_CryptoAssetJointValidatorAgreementThresholdPriorNoticePeriod" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitCommonStockIssuancesDetails" xlink:type="extended" xlink:title="99941102 - Disclosure - Stockholders' Equity (Deficit) - Common Stock Issuances (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityTable" xlink:label="hypd_StockholdersEquityTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_StockholdersEquityTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_May2026PublicEquityIssuanceMember" xlink:label="hypd_May2026PublicEquityIssuanceMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_May2026PublicEquityIssuanceMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="hypd_StockholdersEquityTable" xlink:to="us-gaap_StatementClassOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityLineItems" xlink:label="hypd_StockholdersEquityLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="hypd_StockholdersEquityTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockDividendsShares" xlink:label="us-gaap_PreferredStockDividendsShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockDividendsShares" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConversionOfStockSharesConverted1" xlink:label="us-gaap_ConversionOfStockSharesConverted1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_ConversionOfStockSharesConverted1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ConversionOfStockSharesIssued1" xlink:label="us-gaap_ConversionOfStockSharesIssued1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_ConversionOfStockSharesIssued1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockSharesOutstanding" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockConsiderationReceivedOnTransaction" xlink:label="us-gaap_SaleOfStockConsiderationReceivedOnTransaction" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_SaleOfStockConsiderationReceivedOnTransaction" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitAtMarketProgramDetails" xlink:type="extended" xlink:title="99941103 - Disclosure - Stockholders' Equity (Deficit) - At-The-Market Program (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityTable" xlink:label="hypd_StockholdersEquityTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_StockholdersEquityTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_AtMarketOfferingProgramMember" xlink:label="hypd_AtMarketOfferingProgramMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="hypd_AtMarketOfferingProgramMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityLineItems" xlink:label="hypd_StockholdersEquityLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="hypd_StockholdersEquityTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PaymentsOfStockIssuanceCosts" xlink:label="us-gaap_PaymentsOfStockIssuanceCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PaymentsOfStockIssuanceCosts" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitSeriesPreferredStockSecuritiesPurchaseAgreementsDetails" xlink:type="extended" xlink:title="99941104 - Disclosure - Stockholders' Equity (Deficit) - Series A Preferred Stock Securities Purchase Agreements (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityTable" xlink:label="hypd_StockholdersEquityTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="us-gaap_ClassOfWarrantOrRightAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_StockholdersEquityTable" xlink:to="us-gaap_ClassOfWarrantOrRightAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="us-gaap_ClassOfWarrantOrRightDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_ClassOfWarrantOrRightAxis" xlink:to="us-gaap_ClassOfWarrantOrRightDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_InvestorWarrantsMember" xlink:label="hypd_InvestorWarrantsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_InvestorWarrantsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_PlacementAgentWarrantsMember" xlink:label="hypd_PlacementAgentWarrantsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_PlacementAgentWarrantsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="us-gaap_StatementClassOfStockAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="hypd_StockholdersEquityTable" xlink:to="us-gaap_StatementClassOfStockAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementClassOfStockAxis" xlink:to="us-gaap_ClassOfStockDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SeriesAPreferredStockMember" xlink:label="us-gaap_SeriesAPreferredStockMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ClassOfStockDomain" xlink:to="us-gaap_SeriesAPreferredStockMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityLineItems" xlink:label="hypd_StockholdersEquityLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="hypd_StockholdersEquityTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_SharesIssuedPricePerShare" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ProceedsFromIssuanceOfPreferredStockAndWarrantsPrivatePlacement" xlink:label="hypd_ProceedsFromIssuanceOfPreferredStockAndWarrantsPrivatePlacement" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="hypd_ProceedsFromIssuanceOfPreferredStockAndWarrantsPrivatePlacement" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockConvertibleConversionRatio" xlink:label="us-gaap_PreferredStockConvertibleConversionRatio" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockConvertibleConversionRatio" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_WarrantsAndRightsOutstandingTerm" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_WarrantsAndRightsOutstandingTerm" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockSharesAuthorized" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockDividendRatePercentage" xlink:label="us-gaap_PreferredStockDividendRatePercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockDividendRatePercentage" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockLiquidationPreferenceValue" xlink:label="us-gaap_PreferredStockLiquidationPreferenceValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="13" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_PreferredStockLiquidationPreferenceValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="14" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodValueIssuedForServices" xlink:label="us-gaap_StockIssuedDuringPeriodValueIssuedForServices" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="15" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueIssuedForServices" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" xlink:label="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="16" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesIssuedForServices" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitStockBasedCompensationExpenseDetails" xlink:type="extended" xlink:title="99941105 - Disclosure - Stockholders' Equity (Deficit) - Stock-Based Compensation Expense (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementOfIncomeLocationBalanceAxis" xlink:label="us-gaap_StatementOfIncomeLocationBalanceAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_StatementOfIncomeLocationBalanceAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitStockBasedCompensationExpenseDefaultDetails" xlink:type="extended" xlink:title="41105 - Disclosure - Stockholders' Equity (Deficit) - Stock-Based Compensation Expense Default (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitWarrantsDetails" xlink:type="extended" xlink:title="99941106 - Disclosure - Stockholders' Equity (Deficit) - Warrants (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:label="us-gaap_ClassOfWarrantOrRightTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="us-gaap_ClassOfWarrantOrRightAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ClassOfWarrantOrRightTable" xlink:to="us-gaap_ClassOfWarrantOrRightAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="us-gaap_ClassOfWarrantOrRightDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_ClassOfWarrantOrRightAxis" xlink:to="us-gaap_ClassOfWarrantOrRightDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice3.2500Member" xlink:label="hypd_ExercisePrice3.2500Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice3.2500Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice4.0000Member" xlink:label="hypd_ExercisePrice4.0000Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice4.0000Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice5.2720Member" xlink:label="hypd_ExercisePrice5.2720Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice5.2720Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice8.6080Member" xlink:label="hypd_ExercisePrice8.6080Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice8.6080Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice197.5680Member" xlink:label="hypd_ExercisePrice197.5680Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice197.5680Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice217.9200Member" xlink:label="hypd_ExercisePrice217.9200Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice217.9200Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ExercisePrice380.8000Member" xlink:label="hypd_ExercisePrice380.8000Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_ClassOfWarrantOrRightDomain" xlink:to="hypd_ExercisePrice380.8000Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:label="us-gaap_ClassOfWarrantOrRightLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ClassOfWarrantOrRightIssued" xlink:label="hypd_ClassOfWarrantOrRightIssued" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="hypd_ClassOfWarrantOrRightIssued" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ClassOfWarrantOrRightExercised" xlink:label="hypd_ClassOfWarrantOrRightExercised" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="hypd_ClassOfWarrantOrRightExercised" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ClassOfWarrantOrRightExpired" xlink:label="hypd_ClassOfWarrantOrRightExpired" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="hypd_ClassOfWarrantOrRightExpired" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ClassOfWarrantOrRightOutstanding" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="us-gaap_ClassOfWarrantOrRightOutstanding" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ClassOfWarrantOrRightWeightedAverageRemainingLife" xlink:label="hypd_ClassOfWarrantOrRightWeightedAverageRemainingLife" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="hypd_ClassOfWarrantOrRightWeightedAverageRemainingLife" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ClassOfWarrantOrRightExercisable" xlink:label="hypd_ClassOfWarrantOrRightExercisable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_ClassOfWarrantOrRightLineItems" xlink:to="hypd_ClassOfWarrantOrRightExercisable" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureStockholdersEquityDeficitAdditionalInformationDetails" xlink:type="extended" xlink:title="99941108 - Disclosure - Stockholders' Equity (Deficit) - Additional Information (Details)">
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityTable" xlink:label="hypd_StockholdersEquityTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="hypd_StockholdersEquityTable" xlink:to="us-gaap_AwardTypeAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="us-gaap_RestrictedStockUnitsRSUMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_RestrictedStockUnitsRSUMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_StockholdersEquityLineItems" xlink:label="hypd_StockholdersEquityLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="hypd_StockholdersEquityTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="us-gaap_TreasuryStockSharesAcquired" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="us-gaap_TreasuryStockSharesAcquired" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_TreasuryStockPeriodIncreaseDecrease" xlink:label="hypd_TreasuryStockPeriodIncreaseDecrease" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="hypd_StockholdersEquityLineItems" xlink:to="hypd_TreasuryStockPeriodIncreaseDecrease" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSegmentReportingSignificantExpensesDetails" xlink:type="extended" xlink:title="99941202 - Disclosure - Segment Reporting - Significant expenses (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="us-gaap_StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_OphthalmicTechnologySegmentMember" xlink:label="hypd_OphthalmicTechnologySegmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SegmentDomain" xlink:to="hypd_OphthalmicTechnologySegmentMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsMember" xlink:label="hypd_DigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SegmentDomain" xlink:to="hypd_DigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis" xlink:label="srt_ConsolidationItemsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="srt_ConsolidationItemsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain" xlink:label="srt_ConsolidationItemsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_ConsolidationItemsAxis" xlink:to="srt_ConsolidationItemsDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember" xlink:label="us-gaap_OperatingSegmentsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_ConsolidationItemsDomain" xlink:to="us-gaap_OperatingSegmentsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CorporateAndReconcilingItemsMember" xlink:label="hypd_CorporateAndReconcilingItemsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_ConsolidationItemsDomain" xlink:to="hypd_CorporateAndReconcilingItemsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="us-gaap_SegmentReportingInformationLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfRevenueAbstract" xlink:label="us-gaap_CostOfRevenueAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_CostOfRevenueAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CostOfRevenue" xlink:label="us-gaap_CostOfRevenue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_CostOfRevenueAbstract" xlink:to="us-gaap_CostOfRevenue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GrossProfit" xlink:label="us-gaap_GrossProfit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_GrossProfit" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_OperatingExpensesAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:label="us-gaap_ResearchAndDevelopmentExpenseAbstract" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_ResearchAndDevelopmentExpenseAbstract" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ResearchAndDevelopmentExpenseSalariesAndBenefits" xlink:label="hypd_ResearchAndDevelopmentExpenseSalariesAndBenefits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="hypd_ResearchAndDevelopmentExpenseSalariesAndBenefits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ResearchAndDevelopmentExpenseDirectClinicalAndNonClinicalExpenses" xlink:label="hypd_ResearchAndDevelopmentExpenseDirectClinicalAndNonClinicalExpenses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="hypd_ResearchAndDevelopmentExpenseDirectClinicalAndNonClinicalExpenses" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ResearchAndDevelopmentExpenseFacilitiesExpenses" xlink:label="hypd_ResearchAndDevelopmentExpenseFacilitiesExpenses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="hypd_ResearchAndDevelopmentExpenseFacilitiesExpenses" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ResearchAndDevelopmentExpenseNonCashStockBasedCompensationExpense" xlink:label="hypd_ResearchAndDevelopmentExpenseNonCashStockBasedCompensationExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="hypd_ResearchAndDevelopmentExpenseNonCashStockBasedCompensationExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ResearchAndDevelopmentExpenseSuppliesAndMaterials" xlink:label="hypd_ResearchAndDevelopmentExpenseSuppliesAndMaterials" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="hypd_ResearchAndDevelopmentExpenseSuppliesAndMaterials" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherResearchAndDevelopmentExpense" xlink:label="us-gaap_OtherResearchAndDevelopmentExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="us-gaap_OtherResearchAndDevelopmentExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_ResearchAndDevelopmentExpenseDepreciationExpense" xlink:label="hypd_ResearchAndDevelopmentExpenseDepreciationExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_ResearchAndDevelopmentExpenseAbstract" xlink:to="hypd_ResearchAndDevelopmentExpenseDepreciationExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetAndCryptoAssetReceivableRealizedGainLossOperating" xlink:label="hypd_CryptoAssetAndCryptoAssetReceivableRealizedGainLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="hypd_CryptoAssetAndCryptoAssetReceivableRealizedGainLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetUnrealizedGainLossOperating" xlink:label="us-gaap_CryptoAssetUnrealizedGainLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_CryptoAssetUnrealizedGainLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetReceivableUnrealizedGainLossOperating" xlink:label="hypd_CryptoAssetReceivableUnrealizedGainLossOperating" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="hypd_CryptoAssetReceivableUnrealizedGainLossOperating" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" xlink:label="us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_ImpairmentOfIntangibleAssetsIndefinitelivedExcludingGoodwill" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_GainLossOnDerivativeInstrumentsNetPretax" xlink:label="us-gaap_GainLossOnDerivativeInstrumentsNetPretax" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_GainLossOnDerivativeInstrumentsNetPretax" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" xlink:label="hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="hypd_CryptoAssetsReceivableProvisionReversalForCreditLosses" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_OperatingIncomeLossExcludingReconcilingItems" xlink:label="hypd_OperatingIncomeLossExcludingReconcilingItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="hypd_OperatingIncomeLossExcludingReconcilingItems" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingLeaseImpairmentLoss" xlink:label="us-gaap_OperatingLeaseImpairmentLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_OperatingLeaseImpairmentLoss" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_NonoperatingIncomeExpense" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_NetIncomeLoss" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSegmentReportingSegmentAssetsDetails" xlink:type="extended" xlink:title="99941203 - Disclosure - Segment Reporting - Segment assets (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="us-gaap_StatementBusinessSegmentsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="us-gaap_StatementBusinessSegmentsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentDomain" xlink:label="us-gaap_SegmentDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_StatementBusinessSegmentsAxis" xlink:to="us-gaap_SegmentDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_OphthalmicTechnologySegmentMember" xlink:label="hypd_OphthalmicTechnologySegmentMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SegmentDomain" xlink:to="hypd_OphthalmicTechnologySegmentMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_DigitalAssetsMember" xlink:label="hypd_DigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SegmentDomain" xlink:to="hypd_DigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsAxis" xlink:label="srt_ConsolidationItemsAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:to="srt_ConsolidationItemsAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_ConsolidationItemsDomain" xlink:label="srt_ConsolidationItemsDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_ConsolidationItemsAxis" xlink:to="srt_ConsolidationItemsDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OperatingSegmentsMember" xlink:label="us-gaap_OperatingSegmentsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_ConsolidationItemsDomain" xlink:to="us-gaap_OperatingSegmentsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CorporateAndReconcilingItemsMember" xlink:label="hypd_CorporateAndReconcilingItemsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_ConsolidationItemsDomain" xlink:to="hypd_CorporateAndReconcilingItemsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="us-gaap_SegmentReportingInformationLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetFairValue" xlink:label="us-gaap_CryptoAssetFairValue" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_CryptoAssetFairValue" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_OtherAssets" xlink:label="us-gaap_OtherAssets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_OtherAssets" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_SegmentReportingInformationLineItems" xlink:to="us-gaap_Assets" priority="1" use="optional" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.eyenoviabio.com/role/DisclosureSubsequentEventsDetails" xlink:type="extended" xlink:title="99941301 - Disclosure - Subsequent Events (Details)">
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTable" xlink:label="us-gaap_SubsequentEventTable" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="1" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_SubsequentEventTypeAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="2" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_DebtInstrumentAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HyperlendLoanMember" xlink:label="hypd_HyperlendLoanMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="hypd_HyperlendLoanMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="3" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_KhypeLiquidStakingTokenMember" xlink:label="hypd_KhypeLiquidStakingTokenMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:to="hypd_KhypeLiquidStakingTokenMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusAxis" xlink:label="us-gaap_PledgedStatusAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="4" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_PledgedStatusAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PledgedStatusDomain" xlink:label="us-gaap_PledgedStatusDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_PledgedStatusAxis" xlink:to="us-gaap_PledgedStatusDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_AssetPledgedAsCollateralMember" xlink:label="us-gaap_AssetPledgedAsCollateralMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_PledgedStatusDomain" xlink:to="us-gaap_AssetPledgedAsCollateralMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="5" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_TypeOfArrangementAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeAssetUseServiceAgreementMember" xlink:label="hypd_HypeAssetUseServiceAgreementMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="hypd_HypeAssetUseServiceAgreementMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="6" xlink:from="us-gaap_SubsequentEventTable" xlink:to="srt_CounterpartyNameAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_SkewTechnologiesIncMember" xlink:label="hypd_SkewTechnologiesIncMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="hypd_SkewTechnologiesIncMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_BursaGlobalInc.Member" xlink:label="hypd_BursaGlobalInc.Member" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="hypd_BursaGlobalInc.Member" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetAxis" xlink:label="srt_CryptoAssetAxis" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" order="7" xlink:from="us-gaap_SubsequentEventTable" xlink:to="srt_CryptoAssetAxis" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2026/elts/srt-2026.xsd#srt_CryptoAssetDomain" xlink:label="srt_CryptoAssetDomain" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" order="1" xlink:from="srt_CryptoAssetAxis" xlink:to="srt_CryptoAssetDomain" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_HypeDigitalAssetsMember" xlink:label="hypd_HypeDigitalAssetsMember" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="1" xlink:from="srt_CryptoAssetDomain" xlink:to="hypd_HypeDigitalAssetsMember" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_SubsequentEventLineItems" xlink:label="us-gaap_SubsequentEventLineItems" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" order="1" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_SubsequentEventTable" use="optional" xbrldt:contextElement="segment" xbrldt:closed="true" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsPurchased" xlink:label="hypd_CryptoAssetNumberOfUnitsPurchased" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="2" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsPurchased" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetPurchase" xlink:label="us-gaap_CryptoAssetPurchase" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="3" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_CryptoAssetPurchase" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IndefiniteLivedIntangibleAssetsNumberOfUnits" xlink:label="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="4" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_IndefiniteLivedIntangibleAssetsNumberOfUnitsRedeemedOrSold" xlink:label="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnitsRedeemedOrSold" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="5" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_IndefiniteLivedIntangibleAssetsNumberOfUnitsRedeemedOrSold" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetFairValuePerUnit" xlink:label="hypd_CryptoAssetFairValuePerUnit" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="6" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetFairValuePerUnit" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetNumberOfUnits" xlink:label="us-gaap_CryptoAssetNumberOfUnits" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="7" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_CryptoAssetNumberOfUnits" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CryptoAssetPeriodIncreaseDecrease" xlink:label="us-gaap_CryptoAssetPeriodIncreaseDecrease" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="8" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_CryptoAssetPeriodIncreaseDecrease" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_FinancialInstrumentDelivered" xlink:label="hypd_FinancialInstrumentDelivered" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="9" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_FinancialInstrumentDelivered" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_PreferredStockDividendsShares" xlink:label="us-gaap_PreferredStockDividendsShares" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="10" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_PreferredStockDividendsShares" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetNumberOfUnitsLinkedToTradingWallet" xlink:label="hypd_CryptoAssetNumberOfUnitsLinkedToTradingWallet" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="11" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetNumberOfUnitsLinkedToTradingWallet" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_MarketRevenuesPercentage" xlink:label="hypd_MarketRevenuesPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="12" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_MarketRevenuesPercentage" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementInitialTerm" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementInitialTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="13" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementInitialTerm" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementAutomaticRenewable" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementAutomaticRenewable" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="14" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementAutomaticRenewable" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementTerminatedNotice" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementTerminatedNotice" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="15" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementTerminatedNotice" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="hypd-20260630.xsd#hypd_CryptoAssetHypeAssetUseServiceAgreementThresholdPriorWrittenNoticePeriodForTermination" xlink:label="hypd_CryptoAssetHypeAssetUseServiceAgreementThresholdPriorWrittenNoticePeriodForTermination" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="16" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="hypd_CryptoAssetHypeAssetUseServiceAgreementThresholdPriorWrittenNoticePeriodForTermination" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="17" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentTerm" xlink:label="us-gaap_DebtInstrumentTerm" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="18" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_DebtInstrumentTerm" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="19" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" priority="1" use="optional" />
    <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_DebtInstrumentDecreaseForgiveness" xlink:label="us-gaap_DebtInstrumentDecreaseForgiveness" />
    <link:definitionArc xlink:type="arc" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" order="20" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_DebtInstrumentDecreaseForgiveness" priority="1" use="optional" />
  </link:definitionLink>
</link:linkbase>
