Antonyms of noun possibility

1 of 4 senses of possibility

Sense 2
possibility, possibleness -- (capability of existing or happening or being true; "there is a possibility that his sense of smell has been impaired")
       Antonym of impossibility (Sense 1)
      => impossibility, impossibleness -- (incapability of existing or occurring)

Synonyms/Hypernyms (Ordered by Estimated Frequency) of noun possibility

4 senses of possibility

Sense 1
possibility -- (a future prospect or potential; "this room has great possibilities")
       => expectation, outlook, prospect -- (belief about (or mental picture of) the future)

Sense 2
possibility, possibleness -- (capability of existing or happening or being true; "there is a possibility that his sense of smell has been impaired")
       => being, beingness, existence -- (the state or fact of existing; "a point of view gradually coming into being"; "laws in existence for centuries")

Sense 3
hypothesis, possibility, theory -- (a tentative insight into the natural world; a concept that is not yet verified but that if true would explain certain facts or phenomena; "a scientific hypothesis that survives experimental testing becomes a scientific theory"; "he proposed a fresh theory of alkalis that later was accepted in chemical practices")
       => concept, conception, construct -- (an abstract or general idea inferred or derived from specific instances)

Sense 4
possibility, possible action, opening -- (a possible alternative; "bankruptcy is always a possibility")
       => option, alternative, choice -- (one of a number of things from which only one can be chosen; "what option did I have?"; "there no other alternative"; "my only choice is to refuse")