sombrero vs chapeau

sombrero and chapeau both are nouns.

Word	Noun	Adjective	Verb	Adverb
sombrero	Yes	No	No	No
chapeau	Yes	No	No	No

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

sombrero: a straw hat with a tall crown and broad brim; worn in American southwest and in Mexico
chapeau: headdress that protects the head from bad weather; has shaped crown and usually a brim

Other hypernyms of sombrero include hat, lid.

sombrero (noun)	chapeau (noun)
a straw hat with a tall crown and broad brim; worn in American southwest and in Mexico	headdress that protects the head from bad weather; has shaped crown and usually a brim