availability vs convenience

availability and convenience both are nouns.

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

As nouns, convenience is a hypernym of availability; that is, convenience is a word with a broader meaning than availability:

availability (noun)	convenience (noun)
the quality of being at hand when needed	a device or control that is very useful for a particular job
	a toilet that is available to the public
	the quality of being useful and convenient
	the state of being suitable or opportune