comic opera vs operetta

comic opera and operetta both are nouns.

Word	Noun	Adjective	Verb	Adverb
comic opera	Yes	No	No	No
operetta	Yes	No	No	No

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

comic opera: opera with a happy ending and in which some of the text is spoken
operetta: a short amusing opera

Other hyponyms of comic opera include light opera.

comic opera (noun)	operetta (noun)
opera with a happy ending and in which some of the text is spoken	a short amusing opera