Triage is a medical term for assessing a patient's condition and to prioritize treatment.
In 2372 on stardate 49485.2, Neelix interviewed The Doctor for his A Briefing with Neelix program, the Doctor began his statement with the tasks he had to perform when he received patients, the first of which was triage. (VOY: "Investigations")
In 2372 on stardate 49548.7, The Doctor was forced to open triage facilities in sickbay and Holodeck 2 to accomodate all of the injured crewmembers from the effects of proton bursts. (VOY: "Deadlock")