A circle is a shape consisting of all points in a plane that are a given distance from a given point, the Centre; equivalently it is the curve traced out by a point that moves in a plane so that its distance from a given point is constant. A circle is the same as 360 degree. You can divide a circle into smaller portions. A part of a circle is called an arc and an arc is named according to its angle. Chapter 29 explains parts of a circle, concentric circle, chord of a circle, segment of a circle, arc of a circle and sector of a circle, with illustrations.