immobilization vs American spelling

immobilization and American spelling both are nouns.

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

immobilization (noun)	American spelling (noun)
the act of limiting movement or making incapable of movement	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')
fixation (as by a plaster cast) of a body part in order to promote proper healing