To obtain the degree, people need to pass a special exam, called a doctorate, or by writing a thesis. The requirements vary according to the subject-matter. A doctorate is usually regarded as a higher degree than a bachelor's degree (such as B.A. or B.Sc)
People who have a doctor's degree may use the title "doctor", though in practice it is often used only by medical doctors. Medical doctors examine, diagnose and treat patients. They can specialize in a number of medical areas, such as pediatrics, anesthesiology or cardiology, or they can work as general practice physicians. Becoming a medical doctor requires a doctoral degree in medicine and participating in clinical training. Medical doctors need a licence, and certification may also be required for many specialists.
- Medical doctor or Doctor of Medicine, a person who practices medicine. Degrees vary: M.D. is common in the United States; MRCP is common in the UK, and they are addressed as "doctor" whatever the degree.
- Surgeon, a doctor who performs surgery is in the UK not called "doctor", because the legal qualification is MRCS: Member of the Royal College of Surgeons, and because the profession had a different origin.
- Physiotherapist, a Physiotherapist having Doctor of Physiotherapy is also called Doctor in USA and in countries like India "traditional and conventional use of Doctor" can be used by using "PT" as suffix for B.P.T.(Bachelor of Physiotherapy) degree holders.
- Juris Doctor or Doctor of Law
- Doctor of Philosophy a general degree for any subject which offers a doctorate for research and presentation of a thesis.
- Universities may award doctorates to people who have done a lot in their fields of study: these are called honorary doctorates. There is no set rule for this. Very often, these are abbreviated "Doctor h.c." (for "honoris causa").