Chord

Chord is the straight-line distance from the leading edge to the trailing edge of an aerofoil (wing cross-section). The chord line is the reference line used to measure the angle of attack and define the wing geometry.

The Mean Aerodynamic Chord (MAC) is the average chord of the wing, used as the reference for CG position calculations. CG is typically expressed as a percentage of MAC (e.g., "CG at 25% MAC").