posterior vs posteriority

posterior and posteriority both are nouns.

Word	Noun	Adjective	Verb	Adverb
posterior	Yes	Yes	No	No
posteriority	Yes	No	No	No

posterior (noun)	posteriority (noun)
the fleshy part of the human body that you sit on	the quality of being toward the back or toward the rear end
a tooth situated at the back of the mouth	following in time

posterior (adjective)	posteriority (adjective)
located at or near or behind a part or near the end of a structure
coming at a subsequent time or stage