postmortem vs necropsy

postmortem and necropsy both are nouns.

Word	Noun	Adjective	Verb	Adverb
postmortem	Yes	Yes	No	No
necropsy	Yes	No	No	No

As nouns, postmortem and necropsy are synonyms defined as:

postmortem and necropsy: an examination and dissection of a dead body to determine cause of death or the changes produced by disease

Other synonyms of postmortem include autopsy, PM, post-mortem, post-mortem examination, postmortem examination.

postmortem (noun)	necropsy (noun)
an examination and dissection of a dead body to determine cause of death or the changes produced by disease	an examination and dissection of a dead body to determine cause of death or the changes produced by disease
discussion of an event after it has occurred

postmortem (adjective)	necropsy (adjective)
occurring or done after death
after death or after an event