exacting vs stern

exacting is not a noun while stern is a noun.

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

As adjectives, exacting and stern are synonyms defined as:

Other synonyms of exacting include strict.

exacting (noun)	stern (noun)
	the rear part of a ship
	the fleshy part of the human body that you sit on

exacting (adjective)	stern (adjective)
having complicated nutritional requirements; especially growing only in special artificial cultures	severe and unremitting in making demands
requiring precise accuracy	not to be placated or appeased or moved by entreaty
severe and unremitting in making demands	of a stern or strict bearing or demeanor; forbidding in aspect
	severely simple