indispensability vs indispensable

indispensability is a noun but indispensable is not a noun.

Word	Noun	Adjective	Verb	Adverb
indispensability	Yes	No	No	No
indispensable	No	Yes	No	No

indispensability (noun)	indispensable (noun)
the quality possessed by something that you cannot possibly do without

indispensability (adjective)	indispensable (adjective)
	not to be dispensed with; essential
	absolutely necessary; vitally necessary
	unavoidable