twosome vs duo

twosome and duo both are nouns.

Word	Noun	Adjective	Verb	Adverb
twosome	Yes	No	No	No
duo	Yes	No	No	No

As nouns, twosome and duo are synonyms defined as:

Other synonyms of twosome include couple, duet.

As nouns, twosome and duo are synonyms defined as:

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

twosome (noun)	duo (noun)
a pair who associate with one another	a musical composition for two performers
two items of the same kind	a pair who associate with one another
	two performers or singers who perform together
	two items of the same kind