Duplicate, 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.
2 other Webster entries under this spelling
Duplicate, a.
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.
Duplicate, 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.
Shades of meaning
A copy is as nearly like the original as the copyist has power to make it; a duplicate is exactly like the original; a carbon copy of a typewritten document must be a duplicate; we may have an inaccurate copy, but never an inaccurate duplicate. A facsimile is like the original in appearance; a duplicate is the same as the original in substance and effect; a facsimile of the Declaration of Independence is not a duplicate. A facsimile of a key might be quite useless; a duplicate will open the lock. A counterpart exactly corresponds to another object, but perhaps without design, while a copy is intentional. An imitation is always thought of as inferior to the original; as, an imitation of Milton. A replica is a copy of a work of art by the maker of the original. In law, a copy of an instrument has in itself no authority; the signatures, as well as other matters, may be copied; a duplicate is really an original, containing the same provisions and signed by the same persons, so that it may have in all respects the same force and effect; a transcript is an official copy, authenticated by the signature of the proper officer, and by the seal of the appropriate court. While strictly there could be but one duplicate, the word is now extended to an indefinite number of exact copies. Reproduction is chiefly applied to living organisms.