What do we call doctors who diagnose and treat diseases, perform surgery, and teach preventive health?

The term used for doctors who diagnose and treat diseases, perform surgery, and teach preventive health is "physicians." Physicians are medical professionals who have completed extensive education and training, enabling them to understand a wide range of medical conditions and their treatments. They not only provide care for patients but also play a vital role in educating them about disease prevention and health promotion.

In contrast, nurse practitioners are advanced practice nurses who can diagnose and treat certain conditions, but their training and scope of practice differ from that of physicians. Surgeons are a subset of physicians who specialize specifically in performing surgeries. Clinical specialists may focus on particular areas of medical practice but do not encompass the full breadth of diagnosis, treatment, and health education that physicians do. Thus, the definition of physicians best fits the description provided in the question.