in·com·mut·able /ˌɪnkəˈmjutəbəl/
  (a.)不能交換的,不能變換的
  In·com·mut·a·ble a.  Not commutable; not capable of being exchanged with, or substituted for, another. --Cudworth. -- In*com*mut*a*ble*ness, n. -- In*com*mut*a*bly, adv.
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  incommutable
       adj 1: not subject to alteration or change [ant: commutable]
       2: not interchangeable or able to substitute one for another;
          "a rare incommutable skill"