Parts of a Circle

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  • 0:00 Circles
  • 0:50 Center
  • 1:20 Radius & Diameter
  • 2:10 Chords
  • 2:35 Lesson Summary
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Lesson Transcript
Instructor: Yuanxin (Amy) Yang Alcocer

Amy has a master's degree in secondary education and has taught math at a public charter high school.

After watching this video lesson, you will be able to identify the parts of a circle. You will learn the names of four different parts of a circle along with what each part does for the circle.


In this lesson, we talk about circles. Circles are 2-dimensional shapes made by drawing a curve that is always the same distance from a fixed point. You will find circles everywhere you look. You can't escape them! Look at a car; you'll see that the car sits on four wheels that are in the shape of a circle. Ride your bicycle; you'll see that you are riding on two wheels that are also circles. The bottoms of soda cans are also circle-shaped. Our Earth is in the shape of a circle, as is the sun and moon. I'm sure that if I asked you to make a list of all the circle shapes you see in the room that you are in right now, you would be able to write down at least one, if not more, items that are circle-shaped.

Let's take a look now at four very important terms that describe very important parts of a circle.


The most important part of the circle is the center. This is the fixed point that the curve surrounds.


As the name suggests, this fixed point is right in the middle or center of the circle. This center point is a very important part of the circle because without this point, you won't know where exactly the circle is located. If you know where the center of the circle is, then you will know that the circle surrounds this point.

Radius & Diameter

The next term is the radius of the circle. The radius of the circle is the distance from the center of the circle to the edge.


This radius is the same no matter which direction you go from the center. As long as you go from the center to the outer edge of the circle, the radius is always the same.

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