A padle steamer is a ship or boat driven by a steam engine that uses one or more paddle wheels to develop thrust for propulsion. It is also a type of steamboat. Boats with paddle wheels on the sides are termed sidewheelers, while those with a single wheel on the stern are known as sternwheelers. Paddle steamers usually carry the prefix "PS". Although generally associated with steam power, paddleboats, or paddlewheelers have also been driven by diesel engines, animal power, or human power.