sun hat vs sunhat

sun hat and sunhat both are nouns.

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

As nouns, sun hat and sunhat are synonyms defined as:

sun hat and sunhat: a hat with a broad brim that protects the face from direct exposure to the sun

sun hat (noun)	sunhat (noun)
a hat with a broad brim that protects the face from direct exposure to the sun	a hat with a broad brim that protects the face from direct exposure to the sun