A chord of a curve is a geometric line segment whose endpoints both lie on the curve. A secant or a secant line is the line extension of a chord.

Chords of a circle

Chords of a circle have a few known properties. Here's an incomplete list:

1. Chords are equidistant from the center if and only if their lengths are equal.
2. A chord's perpendicular bisector passes the center.
3. Given chord AB, chord CD, and intersection point P of the line extensions (secant lines) of them, the following about lengths is true: AP·PB = CP·PD (Power of a point theorem )