Someone's or something's counterpart is another person or thing that has a similar function or position in a different place. The Foreign Secretary telephoned his Italian counterpart to protest. someone or something that has the same job or purpose as someone or something else in a different place sb's counterpart
A thing may be applied to another thing so as to fit perfectly, as a seal to its impression; hence, a thing which is adapted to another thing, or which supplements it; that which serves to complete or complement anything; hence, a person or thing having qualities lacking in another; an opposite
a duplicate copy a person or thing having the same function or characteristics as another
[ -"pärt ] (noun.) 15th century. Recorded since 1451, originally as countre part "duplicate of a legal document", from Old French contrepartie, itself from contre "facing, opposite" (from Latin contra 'against') + partie "copy of a person or thing," originally past participle of partir "to divide".