trio vs opus

trio and opus both are nouns.

Word	Noun	Adjective	Verb	Adverb
trio	Yes	No	No	No
opus	Yes	No	No	No

As nouns, opus is a hypernym of trio; that is, opus is a word with a broader meaning than trio:

Other hypernyms of trio include composition, musical composition, piece, piece of music.

trio (noun)	opus (noun)
a musical composition for three performers	a musical work that has been created
three people considered as a unit
a set of three similar things considered as a unit
three performers or singers who perform together
the cardinal number that is the sum of one and one and one