Originally an engine was a mechanical device that converted force into motion.

Actuators convert electrical signals and energy into motion of some kind.

As you can see, an engine has a number of systems that help it do its job of converting fuel into motion.

The extra energy can be converted into molecular motion and lost as heat.

Rack and pinion gears are used to convert rotation into linear motion.

Almost all cars currently use what is called a four-stroke combustion cycle to convert gasoline into motion.

An engine or motor is a machine designed to convert energy into useful mechanical motion.

With less energy devoted to fighting gravity, more of the engine's energy could be converted into motion.

"Engine" was originally a term for any mechanical device that converts force into motion.

Devices converting heat energy into motion are commonly referred to simply as engines.