diopter vs American spelling

diopter and American spelling both are nouns.

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

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