adj., n., & v.
--adj.
1. exactly like something already existing; copied (esp. in large numbers).
2 a having two corresponding parts. b existing in two examples; paired. c twice as large or many; doubled.
--n.
1. a one of two identical things, esp. a copy of an original. b one of two or more specimens of a thing exactly or almost identical.
2 Law a second copy of a letter or document.
3 (in full duplicate bridge or whist) a form of bridge or whist in which the same hands are played successively by different players.
4 archaic a pawnbroker's ticket.
--v.tr.
1. multiply by two; double.
2 a make or be an exact copy of. b make or supply copies of (duplicated the leaflet for distribution).
3 repeat (an action etc.), esp. unnecessarily.
Phrases and idioms:
duplicate ratio Math. the proportion of the squares of two numbers. in duplicate consisting of two exact copies.
Derivatives:
duplicable adj. duplication n.
Etymology: L duplicatus past part. of duplicare (as DUPLEX)