From Latin: sector "a cutter"
Definition: The part of a circle enclosed by two radii of a circle and their intercepted arc. A pie-shaped part of a circle.
Try this Drag one of the orange dots that define the endpoints of the blue arc. The sector of the circle is shown in yellow.

As you can see from the figure above, a sector is a pie-shaped part of a circle. It has two straight sides (the two radius lines), the curved edge defined by the arc, and touches the center of the circle.


Radius The radius of the circle of which the sector is a part
Central Angle The angle subtended by the sector to the center of the circle. See Central Angle of an Arc for more.
Arc length The length around the curved arc that defines the sector (shown in red here). For more on this see Arc length definition.


The area of a sector can be found if you know the radius and the central angle or arc length. For more on this see Area of a sector.
While you are here..

... I have a small favor to ask. Over the years we have used advertising to support the site so it can remain free for everyone. However, advertising revenue is falling and I have always hated the ads. So, would you go to Patreon and become a patron of the site? When we reach the goal I will remove all advertising from the site.

It only takes a minute and any amount would be greatly appreciated. Thank you for considering it!   – John Page

Become a patron of the site at

Other circle topics


Equations of a circle

Angles in a circle