A hospital ward was a department within a hospital or other medical facility where patients were kept for like medical conditions or species.
While searching for Devidians in 1893 San Francisco at Sisters of Hope Infirmary, Jean-Luc Picard pretended to be replacing the burners on a gas lamp, as per city ordinances, so it would be safer in the event of an earthquake. When a doctor protested that there hadn't been an earthquake there in thirty years, Picard left the room, saying, "Well, that takes care of this ward." (TNG: "Time's Arrow, Part II")
In 2373, a Bolian orderly feared that half of a medical facility ward would be lost after Klingons took out the reactor during the Battle of Ajilon Prime. (DS9: "Nor the Battle to the Strong")
The wards on Hospital Ship 4-2 were known as levels. Patients were categorized by the Allocator using the treatment coefficient. (VOY: "Critical Care")