Oncology is the part of medical science that deals with cancer and tumours — how they start, how they grow, how doctors find them, and how they are treated. It is a hospital and university word, not a kitchen-table word. In everyday English people just say “cancer” for the illness; they say oncology when they mean the field, the department, or that kind of medicine. Though actually, oncology is wider than “cut out a lump”: it includes drugs, strong-ray treatment, blood cancers (where there is not one lump you can point to), and care that helps people live with the disease. You will see it on hospital signs. The people who work there are oncologists.