availableness vs availability

availableness and availability both are nouns.

Word	Noun	Adjective	Verb	Adverb
availableness	Yes	No	No	No
availability	Yes	No	No	No

As nouns, availableness and availability are synonyms defined as:

availableness and availability: the quality of being at hand when needed

Other synonyms of availableness include accessibility, handiness.

availableness (noun)	availability (noun)
the quality of being at hand when needed	the quality of being at hand when needed