convertibility
  可改變性,可變換,可兌換
  convertibility
  可轉換性
  Con·vert·i·bil·i·ty n. The condition or quality of being convertible; capability of being exchanged; convertibleness.
     The mutual convertibility of land into money, and of money into land.   --Burke.
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  convertibility
       n : the quality of being exchangeable (especially the ability to
           convert a currency into gold or other currencies without
           restriction) [ant: inconvertibility]