immutability vs unchangingness

immutability and unchangingness both are nouns.

Word	Noun	Adjective	Verb	Adverb
immutability	Yes	No	No	No
unchangingness	Yes	No	No	No

As nouns, unchangingness is a hypernym of immutability; that is, unchangingness is a word with a broader meaning than immutability:

immutability: the quality of being incapable of mutation
unchangingness: the quality of being unchangeable; having a marked tendency to remain unchanged

Other hypernyms of immutability include changelessness, unchangeability, unchangeableness.

immutability (noun)	unchangingness (noun)
the quality of being incapable of mutation	the quality of being unchangeable; having a marked tendency to remain unchanged