Conic section (or simply conic) is a curve obtained as the intersection of the surface of a cone with a plane. The three types of conic section are the hyperbola, the parabola, and the ellipse. The circle is a special case of the ellipse, previously called the fourth type. Planes that pass through the vertex of the cone will intersect the cone in a point, a line or a pair of intersecting lines, called degenerate conics.