grief vs negative stimulus

grief and negative stimulus both are nouns.

Word	Noun	Adjective	Verb	Adverb
grief	Yes	No	No	No
negative stimulus	Yes	No	No	No

As nouns, negative stimulus is a hypernym of grief; that is, negative stimulus is a word with a broader meaning than grief:

grief (noun)	negative stimulus (noun)
something that causes great unhappiness	a stimulus with undesirable consequences
intense sorrow caused by loss of a loved one (especially by death)