fixity vs fixed

fixity is a noun but fixed is not a noun.

Word	Noun	Adjective	Verb	Adverb
fixity	Yes	No	No	No
fixed	No	Yes	No	No

fixity (noun)	fixed (noun)
the quality of being fixed in place as by some firm attachment
the quality of being incapable of mutation

fixity (adjective)	fixed (adjective)
	securely placed or fastened or set
	(of a number) having a fixed and unchanging value
	fixed and unmoving
	incapable of being changed or moved or undone; e.g. "frozen prices"