n.
Geometrical curve, one of the conic section s, consisting of the set of all points the same distance (the radius) from a given point (the centre).
A line connecting any two points on a circle is called a chord, and a chord passing through the centre is called a diameter. The distance around a circle (the circumference) equals the length of a diameter multiplied by 03C0; (see pi ). The area of a circle is the square of the radius multiplied by 03C0; . An arc consists of any part of a circle encompassed by an angle with its vertex at the centre (central angle). Its length is in the same proportion to the circumference as the central angle is to a full revolution.