Brakes are generally applied to rotating axles or wheels, but may also take other forms such as the surface of a moving fluid (flaps deployed into water or air). Some vehicles use a combination of braking mechanisms, such as drag racing cars with both wheel brakes and a parachute, or airplanes with both wheel brakes and drag flaps raised into the air during landing.
A brake is a mechanical device which inhibits motion. The rest of this article is dedicated to various types of vehicular brakes. Most commonly brakes use friction to convert kinetic energy into heat, though other methods of energy conversion may be employed.