An anaesthesiologist (American English) or anaesthetist (British English) is a physician trained in anaesthesia and preoperative medicine. Terminology varies between countries. In the United States, the term anaesthesiologist refers to a physician who has completed an accredited residency program in anaesthesiology after medical school training. By contrast, in the UK, most former Commonwealth countries and in Europe, the word anaesthetist is used to refer only to physicians, while their assistants may be termed anaesthetic nurses, anaesthetic technicians, operating department practitioners or physician associates depending on local practice