<?xml version="1.0" encoding="US-ASCII" standalone="no"?>
    <!-- Field: Doc-Info; Name: Generator; Value: GoFiler Complete; Version: 6.5c -->
    <!-- Field: Doc-Info; Name: VendorURI; Value: https://www.novaworks.com -->
    <!-- Field: Doc-Info; Name: Status; Value: 0x00000000 -->
<link:linkbase xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByIndustrySector" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByIndustrySector" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByGeographicRegion" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByGeographicRegion" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByCreditQuality" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByCreditQuality" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByMaturity" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByMaturity" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByAssetCategory" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByAssetCategory" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByOtherCategory" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByOtherCategory" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingsByOtherCategory2" roleURI="http://xbrl.sec.gov/oef/role/HoldingsByOtherCategory2" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#LargestHoldings" roleURI="http://xbrl.sec.gov/oef/role/LargestHoldings" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ProspectusOnly" roleURI="http://xbrl.sec.gov/rr/role/ProspectusOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#RiskOnly" roleURI="http://xbrl.sec.gov/rr/role/RiskOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#CoregistrantOnly" roleURI="http://xbrl.sec.gov/oef/role/CoregistrantOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#SeriesOnly" roleURI="http://xbrl.sec.gov/oef/role/SeriesOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ClassOnly" roleURI="http://xbrl.sec.gov/oef/role/ClassOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#PerformanceMeasureOnly" roleURI="http://xbrl.sec.gov/rr/role/PerformanceMeasureOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingAssetCategoryOnly" roleURI="http://xbrl.sec.gov/oef/role/HoldingAssetCategoryOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#BroadBasedIndexOnly" roleURI="http://xbrl.sec.gov/oef/role/BroadBasedIndexOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#AdditionalIndexOnly" roleURI="http://xbrl.sec.gov/oef/role/AdditionalIndexOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#IndustrySectorOnly" roleURI="http://xbrl.sec.gov/oef/role/IndustrySectorOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#GeographicRegionOnly" roleURI="http://xbrl.sec.gov/oef/role/GeographicRegionOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#CreditQualityOnly" roleURI="http://xbrl.sec.gov/oef/role/CreditQualityOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#MaturityOnly" roleURI="http://xbrl.sec.gov/oef/role/MaturityOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#Other1CategoryOnly" roleURI="http://xbrl.sec.gov/oef/role/Other1CategoryOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#Other2CategoryOnly" roleURI="http://xbrl.sec.gov/oef/role/Other2CategoryOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#LargestHoldingOnly" roleURI="http://xbrl.sec.gov/oef/role/LargestHoldingOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#SalesLoadOnly" roleURI="http://xbrl.sec.gov/oef/role/SalesLoadOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#HoldingMeasureOnly" roleURI="http://xbrl.sec.gov/oef/role/HoldingMeasureOnly" />
    <link:roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#ValueMeasureOnly" roleURI="http://xbrl.sec.gov/oef/role/ValueMeasureOnly" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" arcroleURI="http://xbrl.org/int/dim/arcrole/all" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#notAll" arcroleURI="http://xbrl.org/int/dim/arcrole/notAll" />
    <link:arcroleRef xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/rr/role/ProspectusOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/rr/role/RiskOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_AllRisksMember" xlink:label="loc_oefAllRisksMember" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_StockMarketAndGeopoliticalRiskMember" xlink:label="loc_bruceStockMarketAndGeopoliticalRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceStockMarketAndGeopoliticalRiskMember" xlink:type="arc" order="0" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_IssuerSpecificChangesRiskMember" xlink:label="loc_bruceIssuerSpecificChangesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceIssuerSpecificChangesRiskMember" xlink:type="arc" order="10" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_ManagementRiskMember" xlink:label="loc_bruceManagementRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceManagementRiskMember" xlink:type="arc" order="20" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_DistressedInvestmentRiskMember" xlink:label="loc_bruceDistressedInvestmentRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceDistressedInvestmentRiskMember" xlink:type="arc" order="30" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_LiquidityRiskMember" xlink:label="loc_bruceLiquidityRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceLiquidityRiskMember" xlink:type="arc" order="40" />
      <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_InterestRateRiskMember" xlink:label="loc_us-gaapInterestRateRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_us-gaapInterestRateRiskMember" xlink:type="arc" order="50" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_ValueRiskMember" xlink:label="loc_bruceValueRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceValueRiskMember" xlink:type="arc" order="60" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_GrowthRiskMember" xlink:label="loc_bruceGrowthRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceGrowthRiskMember" xlink:type="arc" order="70" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_CashInvestmentsRiskMember" xlink:label="loc_bruceCashInvestmentsRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceCashInvestmentsRiskMember" xlink:type="arc" order="80" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_SmallOrMicroCapInvestingRiskMember" xlink:label="loc_bruceSmallOrMicroCapInvestingRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceSmallOrMicroCapInvestingRiskMember" xlink:type="arc" order="90" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_GovernmentSecuritiesRiskMember" xlink:label="loc_bruceGovernmentSecuritiesRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceGovernmentSecuritiesRiskMember" xlink:type="arc" order="100" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_MaturityRiskMember" xlink:label="loc_bruceMaturityRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceMaturityRiskMember" xlink:type="arc" order="110" />
      <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2026/elts/us-gaap-2026.xsd#us-gaap_CreditRiskMember" xlink:label="loc_us-gaapCreditRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_us-gaapCreditRiskMember" xlink:type="arc" order="120" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_ForeignInvestingRiskMember" xlink:label="loc_bruceForeignInvestingRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceForeignInvestingRiskMember" xlink:type="arc" order="130" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_SectorConcentrationRiskMember" xlink:label="loc_bruceSectorConcentrationRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceSectorConcentrationRiskMember" xlink:type="arc" order="140" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_IssuerCybersecurityRiskMember" xlink:label="loc_bruceIssuerCybersecurityRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceIssuerCybersecurityRiskMember" xlink:type="arc" order="150" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_BusinessContinuityRiskMember" xlink:label="loc_bruceBusinessContinuityRiskMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefAllRisksMember" xlink:to="loc_bruceBusinessContinuityRiskMember" xlink:type="arc" order="160" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/CoregistrantOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/SeriesOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2026/dei-2026.xsd#dei_EntityDomain" xlink:label="loc_deiEntityDomain" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_S000011411Member" xlink:label="loc_bruceS000011411Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_deiEntityDomain" xlink:to="loc_bruceS000011411Member" xlink:type="arc" order="0" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ClassOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_ShareClassDomain" xlink:label="loc_oefShareClassDomain" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_C000031584Member" xlink:label="loc_bruceC000031584Member" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefShareClassDomain" xlink:to="loc_bruceC000031584Member" xlink:type="arc" order="0" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/rr/role/PerformanceMeasureOnly">
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/oef/2026/oef-2026.xsd#oef_PerformanceMeasureDomain" xlink:label="loc_oefPerformanceMeasureDomain" />
      <link:loc xlink:type="locator" xlink:href="bruce-20261026.xsd#bruce_SAndP500StockIndexReflectsNoDeductionForFeesMember" xlink:label="loc_bruceSAndP500StockIndexReflectsNoDeductionForFeesMember" />
      <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_oefPerformanceMeasureDomain" xlink:to="loc_bruceSAndP500StockIndexReflectsNoDeductionForFeesMember" xlink:type="arc" order="0" />
    </link:definitionLink>
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/HoldingAssetCategoryOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/BroadBasedIndexOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/AdditionalIndexOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/IndustrySectorOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/GeographicRegionOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/CreditQualityOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/MaturityOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/Other1CategoryOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/Other2CategoryOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/LargestHoldingOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/SalesLoadOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/HoldingMeasureOnly" />
    <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/oef/role/ValueMeasureOnly" />
</link:linkbase>
