existence vs existential

existence is a noun but existential is not a noun.

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

existence (noun)	existential (noun)
everything that exists anywhere
the state or fact of existing

existence (adjective)	existential (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