Lift Coefficient
Definition
A wing's efficiency number — how much lift a wing shape generates per unit of airflow.
Symbol: ·
Technical definition
C_l = 2L/(ρv²A). It depends on angle of attack and airfoil shape; lift collapses (stall) when flow separates past the critical angle.
Example
A Cessna wing at cruise runs C_l ≈ 0.4; with flaps down for landing it exceeds 2.0 — the same wing making five times the lift for slow flight.
Common confusion
Lift is not 'because air travels farther over the top' (the equal-transit myth). Lift comes from the wing deflecting air downward — Newton's third law plus pressure differences.