pith helmet vs sun helmet

pith helmet and sun helmet both are nouns.

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

As nouns, pith helmet and sun helmet are synonyms defined as:

pith helmet and sun helmet: a lightweight hat worn in tropical countries for protection from the sun

Other synonyms of pith helmet include pith hat, topee, topi.

pith helmet (noun)	sun helmet (noun)
a lightweight hat worn in tropical countries for protection from the sun	a lightweight hat worn in tropical countries for protection from the sun