Permutable is a word that describes something that can be rearranged or interchanged without changing its fundamental meaning. Its antonyms would be words that describe something that can't be rearranged or interchanged without fundamentally altering its meaning. Some examples include non-interchangeable, invariable, immutable, fixed, unchangeable, and rigid. These words indicate that something is unalterable and not subject to modification or transformation. The opposite of permutable implies that the object or concept is not adaptable or flexible and is set in stone. By understanding the antonyms of permutable, we gain a deeper understanding of the concept of changeability and its limitations.