limpidity
  清澈,透明
  Lim·pid·i·ty n.  The quality or state of being limpid.
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  limpidity
       n 1: free from obscurity and easy to understand; the
            comprehensibility of clear expression [syn: clarity, lucidity,
             pellucidity, clearness] [ant: unclearness, obscureness]
       2: passing light without diffusion or distortion [syn: pellucidness,
           pellucidity]