Drag

Drag is an aerodynamic force exerting a resistance to movement.

Drag is the component of the resultant of aerodynamic forces exerted in the direction of the velocity of the moving body.

For an aircraft, the induced drag is the force induced by the lift. It is due to the finite length of the wing, with a change from two-dimensional aerodynamics to three-dimensional aerodynamics.

At a wing tip the particles have tendency to escape from the regions of high pressure responsible for lift (intrados) to return to low pressure regions. Their circular movement forms the vortex at the wing tip responsible for the induced drag. The ground effect improves the aerodynamic qualities by limiting the formation of vortices.

Wave drag is due to the appearance of a shock wave at transonic flow speeds (in which part of the flow is at a Mach number greater than one).