informality
  非正式
  In·for·mal·i·ty n.; pl. Informalities
  1. The state of being informal; lack of regular, prescribed, or customary form; as, the informality of legal proceedings.
  2. An informal, unconventional, or unofficial act or proceeding; something which is not in proper or prescribed form or does not conform to the established rule.
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  informality
       n 1: a manner that does not take forms and ceremonies seriously
            [ant: formality]
       2: freedom from constraint or embarrassment; "I am never at
          ease with strangers" [syn: ease]