omis·sion /oˈmɪʃən, ə-/
  省略,遺漏,疏忽
  O·mis·sion n.
  1. The act of omitting; neglect or failure to do something required by propriety or duty.
     The most natural division of all offenses is into those of omission and those of commission.   --Addison.
  2. That which is omitted or is left undone.
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  omission
       n 1: a mistake resulting from neglect [syn: skip]
       2: something that has been omitted; "she searched the table for
          omissions"
       3: any process whereby sounds are left out of spoken words or
          phrases [syn: deletion]
       4: neglecting to do something; leaving out or passing over
          something