nonexistence vs void

nonexistence and void both are nouns.

Word	Noun	Adjective	Verb	Adverb
nonexistence	Yes	No	No	No
void	Yes	Yes	Yes	No

As nouns, void is a hyponym of nonexistence; that is, void is a word with a more specific, narrower meaning than nonexistence:

Other hyponyms of nonexistence include irreality, unreality, nihility, nothingness, nullity, impossibility, impossibleness.

nonexistence (noun)	void (noun)
the state of not existing	an empty area or space
	the state of nonexistence

nonexistence (adjective)	void (adjective)
	containing nothing
	lacking any legal or binding force

nonexistence (verb)	void (verb)
	excrete or discharge from the body
	take away the legal force of or render ineffective
	clear (a room, house, place) of occupants or empty or clear (a place or receptacle) of something
	declare invalid