sun vs sunbathe

sun is a noun but sunbathe is not a noun.

Word	Noun	Adjective	Verb	Adverb
sun	Yes	No	Yes	No
sunbathe	No	No	Yes	No

As verbs, sun and sunbathe are synonyms defined as:

sun (noun)	sunbathe (noun)
any star around which a planetary system revolves
the star that is the source of light and heat for the planets in the solar system
a person considered as a source of warmth or energy or glory etc
the rays of the sun

sun (verb)	sunbathe (verb)
expose one's body to the sun	expose one's body to the sun
expose to the rays of the sun or affect by exposure to the sun