A physician, medical practitioner, medical doctor, or simply doctor, is a professional who practices medicine, which is concerned with promoting, maintaining, or restoring health through the study, diagnosis, and treatment of disease, injury, and other physical and mental impairments to the body.
In the United States, Medicare is a single-payer, national social insurance program administered by the US federal government since 1966, currently using about 30–50 private insurance companies across the United States.
Sir William Osler, 1st Baronet, FRS, FRCP (July 12, 1849 – December 29, 1919) was a Canadian physician and one of the four founding professors of Johns Hopkins Hospital. Osler created the first residency program for specialty training of physicians, and he was the first to bring medical students out of the lecture hall for training.