inalterable vs unalterable

inalterable and unalterable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
inalterable	No	Yes	No	No
unalterable	No	Yes	No	No

As adjectives, inalterable and unalterable are synonyms defined as:

inalterable (adjective)	unalterable (adjective)
not capable of being changed or altered	not capable of being changed or altered
	of a sentence; that cannot be changed
	remaining the same for indefinitely long times