sun helmet vs pith hat

sun helmet and pith hat both are nouns.

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

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

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

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

sun helmet (noun)	pith hat (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