Duplicate

a. [Lat. duplicatus, p. p. of duplicare, to double, from duplex, double, twofold; Fr. dupliquer, Fr., Sp., & Pg. duplicar, It. duplicare. See DOUBLE.] Double; twofold.

Duplicate proportion, or ratio (Math.), the proportion or ratio of squares. Thus, in geometrical proportion, the first term to the third is said to be in a duplicate ratio of the first to the second, or as its square is to the square of the second. Thus, in 2, 4, 8, 16, the ratio of 2 to 8 is a duplicate of that of 2 to 4, or as the square of 2 is to the square of 4.

n. 1. That which exactly resembles or corresponds to something else; hence, a copy; a transcript; a counterpart. I send a duplicate both of it and my last dispatch. Sir W. Temple.

2Sense 2. That which is of the same kind or species as some other thing, but not necessarily resembling it in other respects; as, a duplicate of a mineral specimen, and the like.

3Sense 3. (Law.) An original instrument repeated; a document which is the same as another in all essential particulars, and differing from a mere copy in having all the validity of an original. Burrill.