## What is the Chord of a Circle?

The diameter of a circle is a chord that passes through the center of the circle.

The word comes from the Greek word “diametros” which comes from two root words.

The root word “dia” means “across” or “through”. And root word “metron” means “measure”.

Ancient mathematicians chose this word because the diameter of a circle measures the distance across a circle.

## Examples

Is it a chord?

Yes, the purple line segment is a chord because both of its endpoints are on the circumference of the circle.

Is it a chord?

Yes, the yellow line segment is a chord because both of its endpoints are on the circumference of the circle.

The chord passes through the center of the circle so it is also a diameter of the circle.

Is it a chord?

No, the green line segment is not a chord because only one of its endpoints is on the circumference of the circle.

## When Will I Use the Chord of a Circle?

When you calculate the circumference of a circle, you will plug the diameter measurement into the circumference formula.

When you calculate the circumference of a circle, you will plug the diameter measurement into the area formula.