incisive vs keen

incisive is not a noun while keen is a noun.

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

As adjectives, incisive and keen are synonyms defined as:

incisive and keen: having or demonstrating ability to recognize or draw fine distinctions

Other synonyms of incisive include acute, discriminating, knifelike, penetrating, penetrative, piercing, sharp.

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

incisive (adjective)	keen (adjective)
having or demonstrating ability to recognize or draw fine distinctions	excellent
suitable for cutting or piercing	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

incisive (verb)	keen (verb)
	express grief verbally