The concept that as the speed of a moving fluid (liquid or gas) increases, the pressure within that fluid decreases. The total energy in a steadily flowing fluid system is a constant along the flow path. An increase in the fluids speed must therefore be matched by a decrease in its pressure.
Law stating that the speed of a fluid varies inversely with pressure, an increase in speed producing a decrease in pressure (such as a drop in hydraulic pressure as the fluid speeds up flowing through a constriction in a pipe) and vice versa. The principle also explains the pressure differences on each surface of an airfoil, which gives lift to the wing of an aircraft. The principle was named for Swiss mathematician and physicist Daniel Bernoulli.