n. A correspondent part; a part that answers to another, as the several parts or copies of an indenture corresponding to the original; a copy; a duplicate.n. The complement, as a certificate of hiring given by a tenant to his landlord on receiving from him a certificate of letting, or a bought note given to the seller on receiving the sold note.n. A person or thing exactly resembling another or corresponding to another in appearance, character, position, influence, and the like; a representative; a match; a fellow.n. One of two parts which fit each other, as a cipher and its key, or a seal and its impression; hence, a thing that supplements another thing or completes it, or a person having qualities wanting in another, and such as compensate for the other's deficiencies.n. In music, the part to be arranged or used in connection with another: as, the bass is the counterpart to the treble.