opera star vs vocalist

opera star and vocalist both are nouns.

Word	Noun	Adjective	Verb	Adverb
opera star	Yes	No	No	No
vocalist	Yes	No	No	No

As nouns, vocalist is a hypernym of opera star; that is, vocalist is a word with a broader meaning than opera star:

Other hypernyms of opera star include singer, vocaliser, vocalizer.

opera star (noun)	vocalist (noun)
singer of lead role in an opera	a person who sings