grieve vs pity

grieve is not a noun while pity is a noun.

Word	Noun	Adjective	Verb	Adverb
grieve	No	No	Yes	No
pity	Yes	No	Yes	No

As verbs, pity is a hyponym of grieve; that is, pity is a word with a more specific, narrower meaning than grieve:

Other hyponyms of grieve include mourn, compassionate, condole with, feel for, sympathize with.

grieve (noun)	pity (noun)
	the humane quality of understanding the suffering of others and wanting to do something about it
	an unfortunate development
	a feeling of sympathy and sorrow for the misfortunes of others

grieve (verb)	pity (verb)
feel grief	share the suffering of
cause to feel sorrow