stern vs grim

stern is a noun but grim is not a noun.

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

As adjectives, stern and grim are synonyms defined as:

Other synonyms of stern include inexorable, relentless, unappeasable, unforgiving, unrelenting.

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

stern (adjective)	grim (adjective)
severe and unremitting in making demands	shockingly repellent; inspiring horror
not to be placated or appeased or moved by entreaty	filled with melancholy and despondency
of a stern or strict bearing or demeanor; forbidding in aspect	causing dejection
severely simple	not to be placated or appeased or moved by entreaty
	harshly ironic or sinister
	harshly uninviting or formidable in manner or appearance