A sedan is a car with a fixed roof that can seat at least four people, featuring a “three-box” design — one “box” or compartment up front for the engine, one for occupants, and another compartment in back known as the trunk. The Speedwell Motor Co. of Dayton, Ohio, is said to have been the first to use the term sedan to describe a car, its 1911 model (see that old-timey car below). Early sedans might have had two or four doors, but the modern sense of the word is associated with four doors.