noun

one of two or more identical things.

books may be disposed of if they are duplicates

verb

make or be an exact copy of.

information sheets had to be typed and duplicated

copy,photocopy,photostat,xerox,mimeograph,make a photocopy of,take a photocopy of,make a carbon copy of,make a carbon of,make a facsimile of,reproduce,replicate,reprint,run off,repeat,do over again,do again,redo,perform again