Any two-dimensional curve traced by the intersection of a right circular cone with a plane. If the plane is perpendicular to the cone's axis, the resulting curve is a circle. Intersections at other angles result in ellipses, parabolas, and hyperbolas. The conic sections are studied in Euclidean geometry to analyze their physical properties and in analytic geometry to derive their equations. In either context, they have useful applications to optics, antenna design, structural engineering, and architecture.