sunhat vs pith hat

sunhat and pith hat both are nouns.

Word	Noun	Adjective	Verb	Adverb
sunhat	Yes	No	No	No
pith hat	Yes	No	No	No

As nouns, pith hat is a hyponym of sunhat; that is, pith hat is a word with a more specific, narrower meaning than sunhat:

sunhat: a hat with a broad brim that protects the face from direct exposure to the sun
pith hat: a lightweight hat worn in tropical countries for protection from the sun

Other hyponyms of sunhat include pith helmet, sun helmet, topee, topi, sunbonnet.

sunhat (noun)	pith hat (noun)
a hat with a broad brim that protects the face from direct exposure to the sun	a lightweight hat worn in tropical countries for protection from the sun