existential vs existentialism

existential is not a noun while existentialism is a noun.

Word	Noun	Adjective	Verb	Adverb
existential	No	Yes	No	No
existentialism	Yes	No	No	No

existential (noun)	existentialism (noun)
	(philosophy) a 20th-century philosophical movement chiefly in Europe; assumes that people are entirely free and thus responsible for what they make of themselves

existential (adjective)	existentialism (adjective)
relating to or dealing with existence (especially with human existence)
of or as conceived by existentialism
derived from experience or the experience of existence