phase modulation vs PM

phase modulation and PM both are nouns.

Word	Noun	Adjective	Verb	Adverb
phase modulation	Yes	No	No	No
PM	Yes	No	No	No

As nouns, phase modulation and PM are synonyms defined as:

phase modulation (noun)	PM (noun)
modulation of the phase of the carrier wave	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