multiply vs duplicate

multiply is not a noun while duplicate is a noun.

Word	Noun	Adjective	Verb	Adverb
multiply	No	No	Yes	Yes
duplicate	Yes	Yes	Yes	No

As verbs, duplicate is a hyponym of multiply; that is, duplicate is a word with a more specific, narrower meaning than multiply:

Other hyponyms of multiply include double, treble, triple, quadruple, quintuple, proliferate.

multiply (noun)	duplicate (noun)
	a copy that corresponds to an original exactly
	something additional of the same kind

multiply (adjective)	duplicate (adjective)
	being two identical
	identically copied from an original

multiply (verb)	duplicate (verb)
have young (animals) or reproduce (organisms)	increase twofold
have offspring or produce more individuals of a given animal or plant	make or do or perform again
combine or increase by multiplication	make a duplicate or duplicates of
make multiple copies of	duplicate or match
combine by multiplication

multiply (adverb)	duplicate (adverb)
in several ways; in a multiple manner