Statement that the speed of a fluid varies
inversely with the 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
aerofoil, which gives lift to the wing of an
aircraft. The principle was named after the
Swiss physicist Daniel Bernoulli.