fixing vs spaying

fixing and spaying both are nouns.

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

As nouns, spaying is a hyponym of fixing; that is, spaying is a word with a more specific, narrower meaning than fixing:

Other hyponyms of fixing include castration, emasculation.

fixing (noun)	spaying (noun)
the act of putting something in working order again	neutering a female by removing the ovaries
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