In general, any combination of bodies so connected that
   their relative motions are constrained, and by means of which force and
   motion may be transmitted and modified, as a screw and its nut, or a
   lever arranged to turn about a fulcrum or a pulley about its pivot,
   etc.; especially, a construction, more or less complex, consisting of a
   combination of moving parts, or simple mechanical elements, as wheels,
   levers, cams, etc., with their supports and connecting framework,
   calculated to constitute a prime mover, or to receive force and motion
   from a prime mover or from another machine, and transmit, modify, and
   apply them to the production of some desired mechanical effect or work,
   as weaving by a loom, or the excitation of electricity by an electrical
   machine.