Synonyms and related words :
changeless, constant, immutable, incommutable, indefeasible, inert, insusceptible of change, intransmutable, invariable, irredeemable, irretrievable, irreversible, irrevocable, lasting, noble, nonreturnable, nonreversible, permanent, reverseless, unalterable, unalterative, unaltered, unchangeable, unchanged, unchanging, undeflectable, undeviating, unmodifiable, unpayable, unremitting, unrestorable, unreturnable, unsusceptible, unvariable, unvarying