Synonyms and related words :
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