in·al·ter·able /(ˌ)ɪˈnɔlt(ə)rəbəl/
  (a.)不能變更的,不變的
  In·al·ter·a·ble a.  Not alterable; incapable of being altered or changed; unalterable. -- In*al*ter*a*ble*ness, n. -- In*al*ter*a*bly, adv.
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  inalterable
       adj : not capable of being changed or altered; "unalterable
             resolve"; "an unalterable ground rule" [syn: unalterable]
             [ant: alterable]