Nurse practitioner: A registered nurse (RN) who has completed an advanced training program in a medical specialty such as pediatrics or internal medicine. Abbreviated NP. An NP may function as a primary direct provider of health care and prescribe medications. An NP may fill another role such as in research rather than in patient care. NPs may treat both mental and physical conditions. In the U.S., NPs are licensed by the individual states in which they practice.

The term "nurse practitioner" encompasses the adult nurse practitioner, advanced practice nurse, certified nurse midwife, certified nurse practitioner, certified registered nurse anesthetist, clinical nurse specialist, clinical specialist in mental health nursing, family nurse practitioner, gerontological nurse practitioner, neonatal nurse practitioner, pediatric nurse practitioner, and school nurse practitioner.