### Topic Page: Circumference

**circumference**

*The Hutchinson Unabridged Encyclopedia with Atlas and Weather Guide*

In geometry, the curved line that encloses a curved plane figure, for example a circle or an ellipse. Its length varies according to the nature of the curve, and may be ascertained by the appropriate formula. The circumference of a circle is πd or 2πr, where d is the diameter of the circle, r is its radius, and π is the constant pi, approximately equal to 3.1416.

essays

Circles: working out area, diameter and radius

Beam me up, Scotty – Finding the Circumference of a Circle

images

circle

### Related Articles

##### Full text Article circumference

/suhkumfərəns/ noun 1 the perimeter of a circle. 2 the external boundary or surface of a figure or object circumferential ...

##### Full text Article circumference

1. The length of a circle, equal to 2πr , where r is the radius. 2. (of a sphere) The length of a great circle on the sphere. ...

##### Full text Article epicycloid

In geometry, a curve resembling a series of arches traced out by a point on the circumference of a circle that rolls around another circle of a diffe