falsity vs illusoriness

falsity and illusoriness both are nouns.

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

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

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

Other hyponyms of falsity include spuriousness, apocryphalness, misleadingness.

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