water vapor vs American spelling

water vapor and American spelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
water vapor	Yes	No	No	No
American spelling	Yes	No	No	No

water vapor (noun)	American spelling (noun)
water in a vaporous form diffused in the atmosphere but below boiling temperature	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')