A simple machine is a mechanical device that changes the direction and/or magnitude of a force. In general, they can be defined as the simplest mechanisms that use leverage (also called mechanical advantage) to multiply force. Six type of simple machines Usually the term refers to the six classical simple machines which were defined by Renaissance scientists: 1. Lever 2. Wheel and axle 3. Pulley 4. Inclined plane 5. Wedge 6. Screw