opera hat vs chapeau

opera hat and chapeau both are nouns.

Word	Noun	Adjective	Verb	Adverb
opera hat	Yes	No	No	No
chapeau	Yes	No	No	No

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

opera hat: a man's hat with a tall crown; usually covered with silk or with beaver fur
chapeau: headdress that protects the head from bad weather; has shaped crown and usually a brim

Other hypernyms of opera hat include hat, lid, man's clothing.

opera hat (noun)	chapeau (noun)
a man's hat with a tall crown; usually covered with silk or with beaver fur	headdress that protects the head from bad weather; has shaped crown and usually a brim