Four-wheel rive, 4WD, or 4x4 ("four by four") is a four-wheeled vehicle with a drivetrain that allows all four wheels to receive torque from the engine simultaneously. In the United States, these cars are often, but not always, included in the broader sport utility vehicle category. While many people associate the term with off-road vehicles, powering all four wheels provides better control in normal road cars on many surfaces, and is an important part of rally racing. In some mechanic circles the term "4 by 4" also denotes the number of drive wheels and the number of speeds the car has, so the term "5 by 4" would denote an automobile with 5 speeds and 4 drive wheels.