rigor vs American spelling

rigor and American spelling both are nouns.

Word	Noun	Adjective	Verb	Adverb
rigor	Yes	No	No	No
American spelling	Yes	No	No	No

rigor (noun)	American spelling (noun)
something hard to endure	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')
the quality of being valid and rigorous
excessive sternness