implacable vs stern

implacable is not a noun while stern is a noun.

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

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

implacable (adjective)	stern (adjective)
incapable of being placated	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