death vs mortification

death and mortification both are nouns.

Word	Noun	Adjective	Verb	Adverb
death	Yes	No	No	No
mortification	Yes	No	No	No

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

death: the permanent end of all life functions in an organism or part of an organism
mortification: the localized death of living cells (as from infection or the interruption of blood supply)

Other hyponyms of death include cell death, necrobiosis, gangrene, necrosis, sphacelus, brain death, cerebral death.

death (noun)	mortification (noun)
the act of killing	(Christianity) the act of mortifying the lusts of the flesh by self-denial and privation (especially by bodily pain or discomfort inflicted on yourself)
the event of dying or departure from life	an instance in which you are caused to lose your prestige or self-respect
the permanent end of all life functions in an organism or part of an organism	strong feelings of embarrassment
the absence of life or state of being dead	the localized death of living cells (as from infection or the interruption of blood supply)
a final state
the time when something ends
the time at which life ends; continuing until dead