perceptive vs keen

perceptive is not a noun while keen is a noun.

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

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

perceptive (adjective)	keen (adjective)
having the ability to perceive or understand; keen in discernment	excellent
of or relating to perception	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

perceptive (verb)	keen (verb)
	express grief verbally