# Definition:Chord

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## Definition

### Chord of a Circle

A **chord** of a circle is a straight line segment whose endpoints are on the circumference of the circle.

In the diagram above, the lines $CD$ and $EF$ are both **chords**.

### Chord of an Ellipse

A **chord** of an ellipse is a straight line segment whose endpoints are on the perimeter of the ellipse.

In the diagram above, the line $AB$ is a **chord**.

### Chord of a Polygon

A **chord** of a polygon $P$ is a straight line connecting two non-adjacent vertices of $P$:

In the above diagram, $DF$ is a **chord** of polygon $ABCDEFG$.

### Chord of a Parabola

A **chord** of a parabola is a straight line segment whose endpoints are on the parabola.

In the diagram above, the lines $AB$ and $C$ are **chords**.

### Chord of a general Curve

There are other sorts of chords, still to be documented.

## Also see

- Results about
**chords**can be found here.

## Sources

- 1998: David Nelson:
*The Penguin Dictionary of Mathematics*(2nd ed.) ... (previous) ... (next): Entry:**chord** - 2008: David Nelson:
*The Penguin Dictionary of Mathematics*(4th ed.) ... (previous) ... (next): Entry:**chord**