opera vs opera house

opera and opera house both are nouns.

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

As nouns, opera and opera house are synonyms defined as:

opera (noun)	opera house (noun)
a building where musical dramas are performed	a building where musical dramas are performed
a drama set to music; consists of singing with orchestral accompaniment and an orchestral overture and interludes