insufficiency vs insufficient

insufficiency is a noun but insufficient is not a noun.

Word	Noun	Adjective	Verb	Adverb
insufficiency	Yes	No	No	No
insufficient	No	Yes	No	No

insufficiency (noun)	insufficient (noun)
lack of an adequate quantity or number
(pathology) inability of a bodily part or organ to function normally
a lack of competence

insufficiency (adjective)	insufficient (adjective)
	of a quantity not able to fulfill a need or requirement