possibility vs expectation

possibility and expectation both are nouns.

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

As nouns, expectation is a hypernym of possibility; that is, expectation is a word with a broader meaning than possibility:

Other hypernyms of possibility include outlook, prospect.

possibility (noun)	expectation (noun)
a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena	belief about (or mental picture of) the future
a possible alternative	the sum of the values of a random variable divided by the number of values
a future prospect or potential	the feeling that something is about to happen
capability of existing or happening or being true	anticipating with confidence of fulfillment