How is the "coefficient of lift" best defined?

The coefficient of lift is best defined as a dimensionless number indicating lift characteristics. This value plays a critical role in aerodynamics, as it quantifies the lift generated by an airfoil or wing at a given angle of attack and airflow conditions. The coefficient of lift is influenced by factors such as the shape of the airfoil, the angle of attack, and the Reynolds number, which characterizes flow conditions over the airfoil.

Being a dimensionless number means it does not have any unit measurements attached to it, allowing for comparisons across different aircraft and conditions. This enables pilots and engineers to predict how changes in variables (like angle of attack or airspeed) will affect lift, making it essential for understanding flight dynamics and aircraft performance.

In contrast, the other options relate to entirely different concepts, such as weight capacity, engine performance, and fuel efficiency calculations, which are not directly associated with the aerodynamic characteristics of lift.