The obvious answer here is that a physician—a doctor of medicine (MD)—treats humans and a veterinarian—a doctor of veterinary medicine (DVM)—treats animals. The two disciplines are intrinsically different: Human care differs from animal care. However, both MDs and DVMs deal with biology and the biological and biomedical sciences, both deal with medicine and health care, and both must complete four years of medical education requiring rigorous academic and personal discipline. After getting their degrees, however, physicians must do at least three extra years of residency to complete their education, while vets do not.