inaccessible vs accessibility

inaccessible is not a noun while accessibility is a noun.

Word	Noun	Adjective	Verb	Adverb
inaccessible	No	Yes	No	No
accessibility	Yes	No	No	No

inaccessible (noun)	accessibility (noun)
	the quality of being at hand when needed
	the attribute of being easy to meet or deal with

inaccessible (adjective)	accessibility (adjective)
capable of being reached only with great difficulty or not at all
not capable of being obtained