keen vs incisive

keen is a noun but incisive is not a noun.

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

As adjectives, keen and incisive are synonyms defined as:

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

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

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

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

keen (verb)	incisive (verb)
express grief verbally