A rotary engine is a type of internal combustion engine that uses a rotating design to convert pressure into rotating motion. Unlike traditional piston engines, which have multiple moving parts, a rotary engine typically has a triangular rotor that moves in an oval chamber, allowing for a more compact and lightweight design. This engine design is often associated with Mazda, which popularized the Wankel rotary engine in vehicles like the Mazda RX-7. Rotary engines are known for their smooth operation and high power-to-weight ratio, but they can have higher fuel consumption and emissions compared to conventional engines.