Fluid power is the use of fluids under pressure to generate, control, and transmit power. Fluid power is subdivided into
hydraulics using a liquid such as
mineral oil or
water, and
pneumatics using a gas such as air or other gases. Compressed-air and water-pressure systems were once used to transmit power from a central source to industrial users over extended geographic areas; fluid power systems today are usually within a single building or mobile machine.