American spelling vs diopter

American spelling and diopter both are nouns.

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

American spelling (noun)	diopter (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')	a unit of measurement of the refractive power of a lens which is equal to the reciprocal of the focal length measured in meters; used by oculists