pos·te·ri·or·i·ty /(ˌ)poˌstɪriˈɔrəti, (ˌ)pɑ, ˈɑr-/
  後天性,在後
  Pos·te·ri·or·i·ty n.  The state of being later or subsequent; as, posteriority of time, or of an event; -- opposed to priority.
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  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]