whitening
  弄白,變白,白粉
  Whit·en·ing n.
  1. The act or process of making or becoming white.
  2. That which is used to render white; whiting.  [R.]
  Whitening stone, a sharpening and polishing stone used by cutlers; also, a finishing grindstone of fine texture.
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  Whit·en v. i. [imp. & p. p. Whitened p. pr. & vb. n. Whitening.]  To grow white; to turn or become white or whiter; as, the hair whitens with age; the sea whitens with foam; the trees in spring whiten with blossoms.
  whitening
       n : changing to a lighter color [syn: lightening]