A registered nurse who is approved by the Board of Nursing to practice nursing in a specified area of advanced nursing practice. APRN is an umbrella term given to a registered nurse who has met advanced educational and clinical practice requirements beyond the two to four years of basic nursing education required of all RNs. There are four types: 1) certified registered nurse anesthetist (CRNA); 2) clinical nurse specialist (CNS); 3) certified nurse practitioner (CNP); and 4), certified nurse midwife (CNM).