retentive vs retentiveness

retentive is not a noun while retentiveness is a noun.

Word	Noun	Adjective	Verb	Adverb
retentive	No	Yes	No	No
retentiveness	Yes	No	No	No

retentive (noun)	retentiveness (noun)
	the property of retaining possessions that have been acquired
	the power of retaining liquid
	the power of retaining and recalling past experience

retentive (adjective)	retentiveness (adjective)
good at remembering
having the capacity to retain something
having the power, capacity, or quality of retaining water