Evanescent /(?)/

Ev·a·nes·cent

Evanescent

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.
  2. Vanishing from notice; imperceptible.
    The difference between right and wrong, in some petty cases, is almost evanescent.