Source : Webster's Revised Unabridged Dictionary (1913)

Posteriority \Pos*te`ri*or"i*ty\, n. [Cf. F.
   post['e]riorit['e].]
   The state of being later or subsequent; as, posteriority of
   time, or of an event; -- opposed to {priority}.

Source : WordNet®

posteriority
     n 1: the quality of being toward the back or toward the rear end
          [ant: {anteriority}]
     2: following in time [syn: {subsequentness}, {subsequence}]
        [ant: {priority}]