Linear actuators are used to convert energy (power from air, electricity, or liquid) into linear motion. These actuators convert rotary motion into linear motion by means of a linear motor, a belt, or a screw drive. The linear actuators that convert energy from air into linear motion are called pneumatic linear actuators; the linear actuators that convert energy from the fluid into linear motion are called hydraulic linear actuators, and the linear actuators that convert energy from electricity to linear motion are referred to as electric linear actuators.