serenade vs opus

serenade and opus both are nouns.

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

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

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

serenade (noun)	opus (noun)
a song characteristically played outside the house of a woman	a musical work that has been created
a musical composition in several movements; has no fixed form

serenade (verb)	opus (verb)
sing and play for somebody