fixedness vs changelessness

fixedness and changelessness both are nouns.

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

As nouns, changelessness is a hypernym of fixedness; that is, changelessness is a word with a broader meaning than fixedness:

fixedness: the quality of being fixed and unchangeable
changelessness: the quality of being unchangeable; having a marked tendency to remain unchanged

Other hypernyms of fixedness include unchangeability, unchangeableness, unchangingness.

fixedness (noun)	changelessness (noun)
the quality of being fixed in place as by some firm attachment	the quality of being unchangeable; having a marked tendency to remain unchanged
the quality of being fixed and unchangeable	the property of remaining unchanged
remaining in place