The word "un-alterable" means something that cannot be changed or modified. Its antonyms include "mutable," "adjustable," "flexible," and "changeable," which refer to things that can be adjusted or modified according to varying circumstances or needs. Other antonyms for "un-alterable" include "transmutable," "modifiable," "transformable," and "convertible." These words all suggest that something can be changed or altered easily or with some effort. In contrast, "un-alterable" is often used to describe things that are permanent, fixed, or unchangeable, such as an unalterable fact or an unalterable law.