\Du"pli*cate\, a. [L. duplicatus, p. p. of duplicare
to double, fr. duplex double, twofold. See {Duplex}.]
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.

\Du"pli*cate\, n.
1. That which exactly resembles or corresponds to something
   else; another, correspondent to the first; hence, a copy;
   a transcript; a counterpart.
         I send a duplicate both of it and my last dispatch.
                                               -- Sir W.
                                               Temple.
2. (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.

\Du"pli*cate\, v. t. [imp. & p. p. {Duplicated}; p.
pr. & vb. n. {Duplicating}.]
1. To double; to fold; to render double.
2. To make a duplicate of (something); to make a copy or
   transcript of. --Glanvill.
3. (Biol.) To divide into two by natural growth or
   spontaneous action; as, infusoria duplicate themselves.