炉子 (lú zi) is a general term for a stove, oven, or furnace — a device that produces heat for cooking, baking, or warming a room. It contrasts with 灶 (zào), which specifically refers to a cooking range or stove top, often built into a kitchen. 炉子 can be a standalone appliance (e.g., a space heater or oven), while 灶 is fixed and used only for cooking.