A chord of a circle is a straight line segment whose endpoints both lie on a circular arc.
The infinite line extension of a chord is a secant line, or just secant.
Properties of chords of a circle are the following:
Chords are equidistant from the center if and only if their lengths are equal.
Equal chords are subtended by equal angles from the center of the circle.
A chord that passes through the center of a circle is called a diameter and is the longest chord of that specific circle.
If the line extensions (secant lines) of chords AB and CD intersect at a point P, then their lengths satisfy AP·PB = CP·PD (power of a point theorem).
The red segment BX is a chord
(as is the diameter segment AB).
