falsity vs falsify

falsity is a noun but falsify is not a noun.

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

falsity (noun)	falsify (noun)
a false statement
the state of being false or untrue

falsity (verb)	falsify (verb)
	falsify knowingly
	insert words into texts, often falsifying it thereby
	prove false
	make false by mutilation or addition; as of a message or story
	tamper, with the purpose of deception