woman's hat vs chapeau

woman's hat and chapeau both are nouns.

Word	Noun	Adjective	Verb	Adverb
woman's hat	Yes	No	No	No
chapeau	Yes	No	No	No

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

woman's hat: hats for women; the wares sold by a milliner
chapeau: headdress that protects the head from bad weather; has shaped crown and usually a brim

Other hypernyms of woman's hat include hat, lid.

woman's hat (noun)	chapeau (noun)
hats for women; the wares sold by a milliner	headdress that protects the head from bad weather; has shaped crown and usually a brim