Cardiology is the medical study of the heart — and, in hospital life, of the blood vessels that serve it. It is a science and a specialty: the doctors in it are cardiologists. A hospital cardiology department is where people go for heart tests and long-term heart care. Though actually, cutting the heart open is usually cardiac surgery, a related but different branch. Cardiology is a formal, technical word. In everyday talk people just say “the heart clinic” or “heart.”