An increase in the velocity of a fluid that is accompanied by a decrease of pressure. Swiss scientist, Daniel Bernoulli (1700-1782), demonstrated that, in most cases, the pressure in a liquid or gas decreases as the liquid or gas moves faster. This explains in part why a wing lifts an airplane.
The Lift of a Wing
The curved top of a wing creates a longer distance from front to back than the straight bottom. This causes the air on top to travel farther, and thus faster, to reach the back than the air underneath, creating a difference in pressure between the two surfaces.