couple vs duet

couple and duet both are nouns.

Word	Noun	Adjective	Verb	Adverb
couple	Yes	No	Yes	No
duet	Yes	No	No	No

As nouns, couple and duet are synonyms defined as:

Other synonyms of couple include duo, twosome.

As nouns, couple and duet are synonyms defined as:

Other synonyms of couple include brace, couplet, distich, duad, duo, dyad, pair, span, twain, twosome, yoke.

couple (noun)	duet (noun)
a pair who associate with one another	(ballet) a dance for two people (usually a ballerina and a danseur noble)
a pair of people who live together	a musical composition for two performers
(physics) something joined by two equal and opposite forces that act along parallel lines	a pair who associate with one another
two items of the same kind	two performers or singers who perform together
a small indefinite number	two items of the same kind

couple (verb)	duet (verb)
engage in sexual intercourse
link together
bring two objects, ideas, or people together
form a pair or pairs