What does the term "chord" refer to in an airfoil?

The term "chord" in an airfoil specifically refers to a straight line that extends from the leading edge (the front part) to the trailing edge (the back part) of the airfoil's profile. This line represents the distance across the width of the airfoil and is an essential concept in aerodynamics as it helps define the shape and characteristics of the airfoil.

The chord length is significant because it is used in various aerodynamic calculations, such as determining the lift generated by the airfoil and assessing its performance characteristics. The concept of the chord is foundational in understanding how airfoils operate in the flow of air, impacting lift and drag.

The other options mistakenly define aspects related to the properties of an airfoil but do not accurately encapsulate the definition of "chord." The thickness pertains to the airfoil's profile but is not defined by the chord, while the surface area involves the overall measurements of the airfoil, and the bend refers to camber, which pertains to the curvature rather than the chord itself.