esophagus vs American spelling

esophagus and American spelling both are nouns.

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

esophagus (noun)	American spelling (noun)
the passage between the pharynx and the stomach	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')