laugh·ter /ˈlæftɚ/
 U笑,笑聲
 Laugh·ter n.  A movement (usually involuntary) of the muscles of the face, particularly of the lips, with a peculiar expression of the eyes, indicating merriment, satisfaction, or derision, and usually attended by a sonorous and interrupted expulsion of air from the lungs. See Laugh, v. i.
    The act of laughter, which is a sweet contraction of the muscles of the face, and a pleasant agitation of the vocal organs, is not merely, or totally within the jurisdiction of ourselves.   --Sir T. Browne.
    Archly the maiden smiled, and with eyes overrunning with laughter.   --Longfellow.
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 laughter
      n 1: the sound of laughing [syn: laugh]
      2: the activity of laughing; the manifestation of joy or mirth
         of scorn; "he enjoyed the laughter of the crowd"