A simple machine is a mechanical device that changes the direction or magnitude of a force. In general, a simple machine can be defined as one of the simplest mechanisms that provide mechanical advantage. Usually the term refers to the six classical simple machines which were defined by Renaissance scientists: ⁕Lever ⁕Wheel and axle ⁕Pulley ⁕Inclined plane ⁕Wedge ⁕Screw A simple machine is an elementary device that has a specific movement, which can be combined with other devices and movements to form a machine. Thus simple machines are considered to be the "building blocks" of more complicated machines. This analytical view of machines as decomposable into simple machines first arose in the Renaissance as a neoclassical amplification of ancient Greek texts on technology, and is still a central part of engineering in today's age of applied science. For example, wheels, levers, and pulleys are all used in the mechanism of a bicycle. Between the simple machines and complex assemblies, several intermediate classes can be defined, which may be termed "compound machines" or "machine elements". The mechanical advantage of a compound machine is simply the product of the mechanical advantages of the simple machines of which it is composed.
wheel and axle
Complex machines are simply a combination of two or more simple machines. The more machines that are added, the more complex the machine.