circumference

Technical terms used in the geometry of the circle; the area of a circle can be seen to equal πr² by dividing the circle into segments that form a rectangle.

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.