Definition
A straight line segment whose endpoints both lie on the circumference of a circle. A chord connects two points on the circle without passing through the center, unless it is the diameter, which is the longest possible chord.
Plain English
A straight line drawn between any two points on the edge of a circle.
Context Anchor
Seen in aviation math, aircraft geometry, airfoil discussions, and layout drawings that use arcs or circular shapes.
Derivation
From the Latin chorda, meaning 'string' or 'cord' — like the taut string of a bow stretched between two points on a curve. The image of a bowstring across a curved bow is a useful mental picture for what a chord does across a circle.
Why Pilots Care
It provides the geometric foundation for the chord line of a wing or propeller blade.
Analogy
Think of a bow and its string: the curved wood is the circle's edge, and the straight string stretched between the two tips is the chord.
Intuition Check
Do not confuse this with a musical chord. Here, chord means a straight line connecting two points on a circle.
Example Sentence 1
The instructor drew a chord of a circle on the whiteboard to show how the airfoil's chord line is measured from leading edge to trailing edge.
Example Sentence 2
Calculating the chord of a circle helps verify the shape of round fuselage sections during inspection.