theater vs American spelling

theater and American spelling both are nouns.

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

theater (noun)	American spelling (noun)
a building where theatrical performances or motion-picture shows can be presented	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')
the art of writing and producing plays
a region in which active military operations are in progress