spaying vs fixing

spaying and fixing both are nouns.

Word	Noun	Adjective	Verb	Adverb
spaying	Yes	No	No	No
fixing	Yes	No	No	No

As nouns, fixing is a hypernym of spaying; that is, fixing is a word with a broader meaning than spaying:

Other hypernyms of spaying include altering, neutering.

spaying (noun)	fixing (noun)
neutering a female by removing the ovaries	the act of putting something in working order again
	the sterilization of an animal
	(histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body
	restraint that attaches to something or holds something in place