PM vs post-mortem examination

PM and post-mortem examination both are nouns.

Word	Noun	Adjective	Verb	Adverb
PM	Yes	No	No	No
post-mortem examination	Yes	No	No	No

As nouns, PM and post-mortem examination are synonyms defined as:

PM and post-mortem examination: an examination and dissection of a dead body to determine cause of death or the changes produced by disease

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

PM (noun)	post-mortem examination (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
modulation of the phase of the carrier wave
the person who holds the position of head of the government in the United Kingdom