artificial vs imitation

artificial is not a noun while imitation is a noun.

Word	Noun	Adjective	Verb	Adverb
artificial	No	Yes	No	No
imitation	Yes	Yes	No	No

artificial (noun)	imitation (noun)
	copying (or trying to copy) the actions of someone else
	something copied or derived from an original
	the doctrine that representations of nature or human behavior should be accurate imitations
	a representation of a person that is exaggerated for comic effect

artificial (adjective)	imitation (adjective)
contrived by art rather than nature	not genuine or real; being an imitation of the genuine article
artificially formal
not arising from natural growth or characterized by vital processes