backside vs stern

backside and stern both are nouns.

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

As nouns, backside and stern are synonyms defined as:

backside (noun)	stern (noun)
the fleshy part of the human body that you sit on	the rear part of a ship
the side of an object that is opposite its front	the fleshy part of the human body that you sit on

backside (adjective)	stern (adjective)
	severe and unremitting in making demands
	not to be placated or appeased or moved by entreaty
	of a stern or strict bearing or demeanor; forbidding in aspect
	severely simple