irreality vs nonexistence

irreality and nonexistence both are nouns.

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

As nouns, nonexistence is a hypernym of irreality; that is, nonexistence is a word with a broader meaning than irreality:

irreality: the state of being insubstantial or imaginary; not existing objectively or in fact
nonexistence: the state of not existing

Other hypernyms of irreality include nonentity.

irreality (noun)	nonexistence (noun)
the state of being insubstantial or imaginary; not existing objectively or in fact	the state of not existing