being vs possibility

being and possibility both are nouns.

Word	Noun	Adjective	Verb	Adverb
being	Yes	No	No	No
possibility	Yes	No	No	No

As nouns, possibility is a hyponym of being; that is, possibility is a word with a more specific, narrower meaning than being:

being (noun)	possibility (noun)
a living thing that has (or can develop) the ability to act or function independently	a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena
the state or fact of existing	a possible alternative
	a future prospect or potential
	capability of existing or happening or being true