Triage is a medical term for assessing a patient's condition and to prioritize treatment.
In 2368, Doctor Beverly Crusher prepared triages for the wounded crewmembers and survivors of the USS Denver. She built emergency infirmaries in three cargo bays and built teams with all personnel who had a medical background including Toby Russell. (TNG: "Ethics")
In 2372 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")
After the USS Voyager was taken over by the Hirogen in 2374, The Doctor was faced with a high incidence of casualties and a near impossible level of triage. When he was later ordered to treat Hirogen wounded over Voyager personnel, his argument that the first rule of triage states that the critical injuries take priority was overruled. (VOY: "The Killing Game", "The Killing Game, Part II")