A nurse is a healthcare professional who, in collaboration with other members of a health care team, is responsible for: treatment, safety, and recovery of acutely or chronically ill individuals; health promotion and maintenance within families, communities and populations; and, treatment of life-threatening emergencies in a wide range of health care settings. Nurses perform a wide range of clinical and non-clinical functions necessary to the delivery of health care, and may also be involved in medical and nursing research.

Practice as a nurse is often defined by state, provincial or territorial governments. As an example, the province of Ontario classifies nurses into the roles of Registered Practical Nurse, Registered Nurse (general class), and Registered Nurse (extended class). In this respect, the title “nurse” is protected by law within the province, and regulated by legislative statute. Some regions have legislated different or expanded roles for nurses, generating many potential nurse careers.