1. according to need (physicians use PRN in writing prescriptions); - Example: "add water as needed" [syn: as needed, as required, pro re nata, PRN]
WordNet (r) 3.0 (2006):
as required
adv 1: according to need (physicians use PRN in writing
prescriptions); "add water as needed" [syn: as needed,
as required, pro re nata, PRN]