Nurse, registered: A nurse who has completed a 2- to 4-year degree program in nursing. Abbreviated RN. RNs provide direct patient care for acutely or chronically ill patients. RNs may further specialize in a particular area. For example, psychiatric nurses are RNs with special training in working with mentally ill patients, and trauma nurses work with physicians and surgeons to help patients in the emergency room of a hospital. Some RNs also work in health research.