severe vs stern

severe is not a noun while stern is a noun.

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

As adjectives, severe and stern are synonyms defined as:

Other synonyms of severe include austere, stark.

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

severe (adjective)	stern (adjective)
causing fear or anxiety by threatening great harm	severe and unremitting in making demands
intensely or extremely bad or unpleasant in degree or quality	not to be placated or appeased or moved by entreaty
severely simple	of a stern or strict bearing or demeanor; forbidding in aspect
very strong or vigorous	severely simple
very bad in degree or extent
unsparing and uncompromising in discipline or judgment