not variable; not changing or capable of being changed; static or constant.

something that is invariable; a constant.

adjective

changeable , changing , variable , varying

adjective

changeless , consistent , constant , fixed , immovable , immutable , inalterable , inflexible , monotonous , perpetual , regular , rigid , same , set , static , unalterable , unchangeable , unchanging , undiversified , unfailing , uniform , unmodifiable , unrelieved , unvarying , unwavering , equable , invariant , steady , ironclad