The study of cancer. There are five major areas of oncology: etiology, prevention, biology, diagnosis, and treatment. As a clinical discipline, it draws upon a wide variety of medical specialties; as a research discipline, oncology also involves specialists in many areas of biology and in a variety of other scientific areas. The approach to the study of cancer is multidisciplinary because cancer is a fundamental problem in biology. Oncology has led to major progress in the understanding not only of cancer but also of normal biology.