fixture vs immovableness

fixture and immovableness both are nouns.

Word	Noun	Adjective	Verb	Adverb
fixture	Yes	No	No	No
immovableness	Yes	No	No	No

As nouns, immovableness is a hypernym of fixture; that is, immovableness is a word with a broader meaning than fixture:

Other hypernyms of fixture include immovability.

fixture (noun)	immovableness (noun)
the act of putting something in working order again	not capable of being moved or rearranged
an object firmly fixed in place (especially in a household)
the quality of being fixed in place as by some firm attachment
a regular patron