American spelling vs square kilometer

American spelling and square kilometer both are nouns.

Word	Noun	Adjective	Verb	Adverb
American spelling	Yes	No	No	No
square kilometer	Yes	No	No	No

American spelling (noun)	square kilometer (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')	a decimal multiple of the unit of surface area, the square metre, equal to 1,000,000 square meters.