pith helmet vs sunhat

pith helmet and sunhat both are nouns.

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

As nouns, sunhat is a hypernym of pith helmet; that is, sunhat is a word with a broader meaning than pith helmet:

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

Other hypernyms of pith helmet include sun hat.

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