fastening vs fixing

fastening and fixing both are nouns.

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

As nouns, fastening and fixing are synonyms defined as:

fastening and fixing: restraint that attaches to something or holds something in place

Other synonyms of fastening include fastener, holdfast.

fastening (noun)	fixing (noun)
the act of fastening things together	the act of putting something in working order again
restraint that attaches to something or holds something in place	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