illusoriness vs falsity

illusoriness and falsity both are nouns.

Word	Noun	Adjective	Verb	Adverb
illusoriness	Yes	No	No	No
falsity	Yes	No	No	No

As nouns, falsity is a hypernym of illusoriness; that is, falsity is a word with a broader meaning than illusoriness:

illusoriness: The quality of resulting from an illusion; of being deceptive, imaginary, unreal.
falsity: the state of being false or untrue

Other hypernyms of illusoriness include falseness.

illusoriness (noun)	falsity (noun)
The quality of resulting from an illusion; of being deceptive, imaginary, unreal.	a false statement
	the state of being false or untrue