The parabola (from the Greek παραβολή) is a type of regular curve, the intersection of a right circular conical surface and a plane parallel to a generating straight line (slantheight) of that surface. The point on the axis of symmetry that intersects the parabola is called the "vertex". The vertex is the point where the curvature is greatest. Parabolas can open up, down, left, right, or in some other sensible direction. This parabola is not asymptotic to any line besides its directrix.