The Parts of a Circle

Contributor: Meghan Vestal. Lesson ID: 11404

Circles sure look simple. They just go around and around. Did you know circles actually have four parts? If this doesn't strike a "chord" with you, it's time you got a-round to learning about circles!


Geometry, Plane Geometry (2D)

learning style
Kinesthetic, Visual
personality style
Grade Level
Intermediate (3-5), Middle School (6-8)
Lesson Type
Quick Query

Lesson Plan - Get It!


Although it looks simple, a circle has four main parts!

  • Can you find and name them all?

A circle is a set of points that are an equal distance from a center point.

  • Did you know there are four parts to a circle?
  • Did you even know that a circle has parts?

The parts of a circle are as follows:

circle parts

Image by Optimager, via Wikimedia Commons, is licensed under the CC BY-SA 3.0 license

What is each of these parts and why are they important?

  • Diameter A line, or chord, that goes from one side of a circle to the other, and passes through the center of the circle.
  • Radius A line segment that starts at the center of a circle and goes to its edge; half of the diameter.
  • Circumference The distance around the perimeter, or outside, of the circle.
  • Chord A line that goes from one side of a circle to the other.

A fun fact about circles is the diameter is always a chord, but a chord is not always a diameter. A chord must run through the center of a circle to be considered the diameter.

Since you have been introduced to the parts of the circle, move on to the Got It? section to practice labeling the parts of a circle on your own.

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