As adjectives the difference between unmodifiable and changeless
is that unmodifiable is incapable of being modified; immune to modification while changeless is unchanging.
unmodifiable
English
Adjective
(
en adjective)
Incapable of being modified; immune to modification.
Synonyms
* (immune to modification) constant, fixed, immutable, unalterable, unchangeable
Antonyms
* (immune to modification) modifiable