The camber is the curvature of an airfoil.
camber of an airfoil is the curve of its upper and lower surfaces.
This curve is measured by how much it departs from the chord of the
airfoil. Some airfoils have very little camber, i.e., the airfoil
looks flat, while others have a higher degree of camber—the
airfoil has more curve. The term upper camber refers to the camber
of the upper surface of the airfoil. The term lower camber refers
to the camber of the lower surface of the airfoil. When the curve
is away from the chord, the camber is said to be positive. When the
curve is toward the chord, the camber is said to be negative. The
camber of an airfoil causes an increase in velocity and a consequent
decrease in pressure of the stream of air moving over it.