sun hat vs hat

sun hat and hat both are nouns.

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

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

sun hat: a hat with a broad brim that protects the face from direct exposure to the sun
hat: headdress that protects the head from bad weather; has shaped crown and usually a brim

Other hypernyms of sun hat include chapeau, lid.

sun hat (noun)	hat (noun)
a hat with a broad brim that protects the face from direct exposure to the sun	an informal term for a person's role
	headdress that protects the head from bad weather; has shaped crown and usually a brim

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