A machine is any device that uses energy to perform some activity. In common usage, the meaning is that of a device having parts that perform or assist in performing any type of work. A simple machine is a device that transforms the direction or magnitude of a force without consuming any energy. The word "machine" is derived from the Latin machina

Historically, a device required moving parts to be classified as a machine, however the advent of electronics technology has led to the development of devices without moving parts that are considered machines, the computer being the most obvious example.

"Engines" are machines that convert heat or other forms of energy into mechanical energy. Internal combustion engines for example use the expansion of gas caused by heat from an exothermic chemical reaction.

Machines are ubiquitous in a wide variety of industrial, commercial, residential and transportation applications. For instance, those employing hydraulics are useful in manufacturing, construction.