composition vs duo

composition and duo both are nouns.

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

As nouns, duo is a hyponym of composition; that is, duo is a word with a more specific, narrower meaning than composition:

composition (noun)	duo (noun)
the act of creating written works	a musical composition for two performers
musical creation	a pair who associate with one another
something that is created by arranging several things to form a unified whole	two performers or singers who perform together
the way in which someone or something is composed	two items of the same kind
the spatial property resulting from the arrangement of parts in relation to each other and to the whole
an essay (especially one written as an assignment)
a musical work that has been created
art and technique of printing with movable type
a mixture of ingredients