fundament vs posterior

fundament and posterior both are nouns.

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

As nouns, fundament and posterior are synonyms defined as:

fundament and posterior: the fleshy part of the human body that you sit on

fundament (noun)	posterior (noun)
lowest support of a structure	the fleshy part of the human body that you sit on
the fleshy part of the human body that you sit on	a tooth situated at the back of the mouth
the fundamental assumptions from which something is begun or developed or calculated or explained

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