GP vs physician

GP and physician both are nouns.

Word	Noun	Adjective	Verb	Adverb
GP	Yes	No	No	No
physician	Yes	No	No	No

As nouns, physician is a hypernym of GP; that is, physician is a word with a broader meaning than GP:

Other hypernyms of GP include doc, doctor, Dr., MD, medico.

GP (noun)	physician (noun)
a physician who is not a specialist but treats all illnesses	a licensed medical practitioner