अपरिवर्तनीय

immutable

not subject or susceptible to change or variation in form or quality or nature

irreversible

incapable of being reversed

irrevocable

incapable of being retracted or revoked; - Shakespeare

unalterable

not capable of being changed or altered

hard and fast

inalterable

not capable of being changed or altered

inconvertible

used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value

unchangeable

not changeable or subject to change; -Ashley Montagu

unconvertible

used especially of currencies; incapable of being exchanged for or replaced by another currency of equal value

unexchangeable

not suitable to be exchanged