opera house vs theatre

opera house and theatre both are nouns.

Word	Noun	Adjective	Verb	Adverb
opera house	Yes	No	No	No
theatre	Yes	No	No	No

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

opera house: a building where musical dramas are performed
theatre: a building where theatrical performances or motion-picture shows can be presented

Other hypernyms of opera house include house, theater.

opera house (noun)	theatre (noun)
a building where musical dramas are performed	a building where theatrical performances or motion-picture shows can be presented
	the art of writing and producing plays
	a region in which active military operations are in progress