mending vs fixing

mending and fixing both are nouns.

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

As nouns, mending and fixing are synonyms defined as:

Other synonyms of mending include fix, fixture, mend, repair, reparation.

mending (noun)	fixing (noun)
the act of putting something in working order again	the act of putting something in working order again
garments that must be repaired	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