What is meant by "coefficient of lift"?

The coefficient of lift is a dimensionless number that quantifies the lift characteristics of a wing or other lifting surface under specific conditions. It is derived from the lift equation, which relates lift force to factors such as air density, velocity, surface area, and the coefficient of lift itself.

This coefficient is essential in aerodynamics because it allows for the comparison of lift generated by different airfoils regardless of their size or the specific conditions in which they operate. By being dimensionless, it provides a standardized way to evaluate how effective a wing is at generating lift relative to the air conditions and the forces acting on it.

The other options refer to different aerodynamic concepts. The measure of drag generated by a wing pertains to drag coefficients, while a numerical value of an aircraft's weight is simply the weight itself and does not relate directly to lift characteristics. A factor affecting fuel efficiency may involve aspects of lift and drag but does not define the coefficient of lift.