opera vs grand opera

opera and grand opera both are nouns.

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

As nouns, grand opera is a hyponym of opera; that is, grand opera is a word with a more specific, narrower meaning than opera:

opera: a drama set to music; consists of singing with orchestral accompaniment and an orchestral overture and interludes
grand opera: opera in which all the text is sung

Other hyponyms of opera include rock opera, bouffe, comic opera, opera bouffe, opera comique, musical drama.

opera (noun)	grand opera (noun)
a building where musical dramas are performed	opera in which all the text is sung
a drama set to music; consists of singing with orchestral accompaniment and an orchestral overture and interludes