nauseous vs sick

nauseous is not a noun while sick is a noun.

Word	Noun	Adjective	Verb	Adverb
nauseous	No	Yes	No	No
sick	Yes	Yes	Yes	No

As adjectives, nauseous and sick are synonyms defined as:

Other synonyms of nauseous include nauseated, queasy, sickish.

nauseous (noun)	sick (noun)
	people who are sick

nauseous (adjective)	sick (adjective)
feeling nausea; feeling about to vomit	affected by an impairment of normal physical or mental function
causing or able to cause nausea	shockingly repellent; inspiring horror
	having a strong distaste from surfeit
	affected with madness or insanity
	deeply affected by a strong feeling
	(of light) lacking in intensity or brightness; dim or feeble
	feeling nausea; feeling about to vomit

nauseous (verb)	sick (verb)
	eject the contents of the stomach through the mouth