posterior vs caudal

posterior is a noun but caudal is not a noun.

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

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

posterior (adjective)	caudal (adjective)
located at or near or behind a part or near the end of a structure	constituting or relating to a tail
coming at a subsequent time or stage	resembling a tail
	situated in or directed toward the part of the body from which the tail arises

posterior (adverb)	caudal (adverb)
	toward the posterior end of the body