# Perimeter and Area

## Circumference and Area of a Circle

Summary Circumference and Area of a Circle

### Terms Associated with Circles

The circumference of a circle is its "perimeter," or the distance around its edge. If we broke the circle and bent it into one flat line, the length of this line would be its circumference: Circumference of a Circle

The diameter of a circle is a line segment from one point on the edge of the circle to another point on the edge, passing through the center of the circle. It is the longest line segment that cuts across the circle from one point to another. There are many different diameters, but they all have the same length: Diameters of a Circle

The radius of a circle is a line segment from the center of the circle to a point on the edge of the circle. It is half of a diameter, and thus its length is half the length of the diameter. Again, there are many radii, but they all have the same length. In the following diagram, a, b, and c are all radii:  