preservation vs fixing

preservation and fixing both are nouns.

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

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

preservation: a process that saves organic substances from decay
fixing: (histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body

Other hyponyms of preservation include fixation, embalmment, plastination, infrigidation, refrigeration.

preservation (noun)	fixing (noun)
the activity of protecting something from loss or danger	the act of putting something in working order again
an occurrence of improvement by virtue of preventing loss or injury or other change	the sterilization of an animal
a process that saves organic substances from decay	(histology) the preservation and hardening of a tissue sample to retain as nearly as possible the same relations they had in the living body
the condition of being (well or ill) preserved	restraint that attaches to something or holds something in place