unalterability vs fixedness

unalterability and fixedness both are nouns.

Word	Noun	Adjective	Verb	Adverb
unalterability	Yes	No	No	No
fixedness	Yes	No	No	No

As nouns, unalterability and fixedness are synonyms defined as:

unalterability and fixedness: the quality of being fixed and unchangeable

unalterability (noun)	fixedness (noun)
the quality of not being alterable	the quality of being fixed in place as by some firm attachment
the quality of being fixed and unchangeable	the quality of being fixed and unchangeable
	remaining in place