twin vs duplicate

twin and duplicate both are nouns.

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

As adjectives, twin and duplicate are synonyms defined as:

Other synonyms of twin include matching, twinned.

As nouns, duplicate is a hypernym of twin; that is, duplicate is a word with a broader meaning than twin:

Other hypernyms of twin include duplication.

As verbs, twin and duplicate are synonyms defined as:

Other synonyms of twin include parallel.

twin (noun)	duplicate (noun)
a duplicate copy	a copy that corresponds to an original exactly
either of two offspring born at the same time from the same pregnancy	something additional of the same kind

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

twin (verb)	duplicate (verb)
give birth to twins	increase twofold
grow as twins	make or do or perform again
bring two objects, ideas, or people together	make a duplicate or duplicates of
duplicate or match	duplicate or match