(a.) Not capable of being transmuted or changed into another substance.

changeless constant immutable incommutable inconvertible indefeasible inert insusceptible of change invariable irretrievable irreversible irrevocable lasting noble nonreturnable nonreversible permanent reverseless unalterable unalterative unaltered unchangeable unchanged unchanging undeflectable undeviating unmodifiable unremitting unrestorable unreturnable unsusceptible unvariable unvarying