A Machine in its most basic definition is a device that allows a person to do work. Simple machines include the lever, pulley, wedge, screw, inclined plane, and wheel and axle. More complex machines combine the principles of the basic machines in order to achieve greater savings in work. For example, a jet engine is simply a series of wedges arranged on a wheel and axle which cut through the air (thus compressing it) whereupon it is mixed with fuel and ignited in order to produce thrust.
Machines, as defined by French Biochemist and Nobel Laureate Jacques Lucien Monod (1910-1976), are "purposeful aggregates of matter that, utilizing energy, perform specific tasks." By this authoritative definition, living systems are recognized as machines.