American spelling vs medieval

American spelling is a noun but medieval is not a noun.

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

American spelling (noun)	medieval (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')

American spelling (adjective)	medieval (adjective)
	relating to or belonging to the Middle Ages
	as if belonging to the Middle Ages; old-fashioned and unenlightened
	characteristic of the time of chivalry and knighthood in the Middle Ages