ev·a·nes·cent /-sṇt/
  (a.)逐漸消失的,容易消散的,會凋零的
  ev·a·nes·cent /ˌɛvəˈnɛsṇt/ 形容詞
  易消滅的,漸消失的,揮發性的,隱失的(指葉脈)
  Ev·a·nes·cent a.
  1. Liable to vanish or pass away like vapor; vanishing; fleeting; as, evanescent joys.
     So evanescent are the fashions of the world in these particulars.   --Hawthorne.
  2. Vanishing from notice; imperceptible.
     The difference between right and wrong, in some petty cases, is almost evanescent.   --Wollaston.
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  evanescent
       adj : tending to vanish like vapor; "evanescent beauty"