perceptive vs understanding

perceptive is not a noun while understanding is a noun.

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

perceptive (noun)	understanding (noun)
	the capacity for rational thought or inference or discrimination
	the cognitive condition of someone who understands
	an inclination to support or be loyal to or to agree with an opinion
	the statement (oral or written) of an exchange of promises

perceptive (adjective)	understanding (adjective)
having the ability to perceive or understand; keen in discernment	characterized by understanding based on comprehension and discernment and empathy
of or relating to perception