curb vs American spelling

curb and American spelling both are nouns.

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

curb (noun)	American spelling (noun)
the act of restraining power or action or limiting excess	English orthography used in the United States (characterized by 'analyze', 'center', 'usable')
an edge between a sidewalk and a roadway consisting of a line of curbstones (usually forming part of a gutter)
a horse's bit with an attached chain or strap to check the horse

curb (verb)	American spelling (verb)
place restrictions on
keep to the curb
lessen the intensity of; temper; hold in restraint; hold or keep within limits