A machine is a thermodynamic system that uses power to apply forces and control movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to natural biological macromolecules, such as molecular machines.
MACHINE definition: an apparatus consisting of interrelated parts with separate functions, used in the performance of some kind of work. See examples of machine used in a sentence.
You do not use 'machine' to refer to the part of a vehicle that provides the power that makes the vehicle move. This part of a car, bus, lorry, or plane is usually called the engine.
A machine is a mechanical device that uses power to apply force and control motion to perform work efficiently. Machines range from simple tools like pulleys and levers to complex systems like engines, robots, and manufacturing equipment.