grieve vs keen

grieve is not a noun while keen is a noun.

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

grieve (noun)	keen (noun)
	a funeral lament sung with loud wailing

grieve (adjective)	keen (adjective)
	excellent
	intense or sharp
	having or demonstrating ability to recognize or draw fine distinctions
	having a sharp cutting edge or point
	painful as if caused by a sharp instrument

grieve (verb)	keen (verb)
feel grief	express grief verbally
cause to feel sorrow