availability vs availableness

availability and availableness both are nouns.

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

As nouns, availability and availableness are synonyms defined as:

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

Other synonyms of availability include accessibility, handiness.

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