A practitioner of physic, i.e. a specialist in internal medicine, especially as opposed to a surgeon; a practitioner who treats with medication rather than with surgery.
"In the eighteenth century, most physicians relied on herbal remedies and bloodletting because surgery was left entirely to barbers."
In plain English: A physician is a doctor who has finished medical school and is trained to treat sick people.
"The physician listened carefully to my symptoms before prescribing medication."
Usage: In modern everyday usage, physician refers to any medical doctor regardless of their specialty. Avoid using it to mean only an internal medicine specialist unless you are specifically discussing historical contexts or making a technical distinction from surgeons.
The word physician entered English via Old French and Latin, originally deriving from the Ancient Greek term for "knowledge of nature." It eventually replaced the native English words leech or leche, which had previously been used to describe a healer.