anterior vs posterior

anterior and posterior both are nouns.

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

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

anterior (adjective)	posterior (adjective)
of or near the head end or toward the front plane of a body	located at or near or behind a part or near the end of a structure
earlier in time	coming at a subsequent time or stage