In medical terms, PRN is an abbreviation for the Latin term "pro re nata," which means "as needed" or "when necessary". It is commonly used in medical prescriptions to indicate that a medication or treatment should be given only when necessary rather than on a regular schedule. For example, a doctor may write a PRN order for pain medication to be given to a patient as needed for pain relief. PRN can also refer to a type of job position that is not part of a regular work schedule, but rather filled on an as-needed basis. In nursing, PRN nurses are fully licensed professionals who work on-call instead of as full-time employees.