in·com·mut·a·ble 
(ĭn′kə-mytə-bəl)
(ĭn′kə-mytə-bəl)adj.
1. Not able to be exchanged one for another: a rare, incommutable skill.
2. That cannot be altered: an incommutable death sentence.
in′com·mut′a·bili·ty, in′com·muta·ble·ness n.
in′com·muta·bly adv.