amphitheater vs American spelling

amphitheater and American spelling both are nouns.

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

amphitheater (noun)	American spelling (noun)
an oval large stadium with tiers of seats; an arena in which contests and spectacles are held	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')
a sloping gallery with seats for spectators (as in an operating room or theater)