stern vs posterior

stern and posterior both are nouns.

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

As nouns, stern and posterior are synonyms defined as:

stern (noun)	posterior (noun)
the rear part of a ship	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

stern (adjective)	posterior (adjective)
severe and unremitting in making demands	located at or near or behind a part or near the end of a structure
not to be placated or appeased or moved by entreaty	coming at a subsequent time or stage
of a stern or strict bearing or demeanor; forbidding in aspect
severely simple