American spelling vs operating theater

American spelling and operating theater both are nouns.

Word	Noun	Adjective	Verb	Adverb
American spelling	Yes	No	No	No
operating theater	Yes	No	No	No

American spelling (noun)	operating theater (noun)
English orthography used in the United States (characterized by 'analyze', 'center', 'usable')	a room in a hospital equipped for the performance of surgical operations