hat vs headdress

hat and headdress both are nouns.

Word	Noun	Adjective	Verb	Adverb
hat	Yes	No	Yes	No
headdress	Yes	No	No	No

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

hat: headdress that protects the head from bad weather; has shaped crown and usually a brim
headdress: clothing for the head

Other hypernyms of hat include headgear.

hat (noun)	headdress (noun)
an informal term for a person's role	clothing for the head
headdress that protects the head from bad weather; has shaped crown and usually a brim

hat (verb)	headdress (verb)
put on or wear a hat
furnish with a hat