invalidity vs invalidness

invalidity and invalidness both are nouns.

Word	Noun	Adjective	Verb	Adverb
invalidity	Yes	No	No	No
invalidness	Yes	No	No	No

As nouns, invalidity and invalidness are synonyms defined as:

invalidity and invalidness: illogicality as a consequence of having a conclusion that does not follow from the premisses

invalidity (noun)	invalidness (noun)
illogicality as a consequence of having a conclusion that does not follow from the premisses	illogicality as a consequence of having a conclusion that does not follow from the premisses