physician vs Dr.

physician and Dr. both are nouns.

Word	Noun	Adjective	Verb	Adverb
physician	Yes	No	No	No
Dr.	Yes	No	No	No

As nouns, physician and Dr. are synonyms defined as:

Other synonyms of physician include doc, doctor, MD, medico.

physician (noun)	Dr. (noun)
a licensed medical practitioner	a licensed medical practitioner
	a person who holds Ph.D. degree (or the equivalent) from an academic institution