fixed vs fixity

fixed is not a noun while fixity is a noun.

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

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

fixed (adjective)	fixity (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"