retral vs posterior

retral is not a noun while posterior is a noun.

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

retral (noun)	posterior (noun)
	the fleshy part of the human body that you sit on
	a tooth situated at the back of the mouth

retral (adjective)	posterior (adjective)
moving or directed or tending in a backward direction or contrary to a previous direction	located at or near or behind a part or near the end of a structure
at or near or toward the posterior	coming at a subsequent time or stage