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