A machine is an assemblage of parts that transmit forces, motion, and energy in a predetermined manner.
A machine is a device to transfer and transforms motion and force from source to load.
A machine is a combination of rigid or resistant bodies, formed and connected so that they move with definite relative motions and transmit force from the source of power to the resistance to be overcome.
A machine has two functions: transmitting definite relative motion and transmitting force.
These functions require strength and rigidity to transmit the forces.
Simple machines include any of various elementary mechanisms having the elements of which all machines are composed.
Included in this category are the lever, the wheel and axle, the pulley, the inclined plane, the wedge, and the screw.