grim vs stern

grim is not a noun while stern is a noun.

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

As adjectives, grim and stern are synonyms defined as:

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

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

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