- a plane curve formed by the intersection of a right circular cone with a plane parallel to a generator of the cone; the set of points in a plane that are equidistant from a fixed line and a fixed point in the same plane or in a parallel plane. Equation: y2 = 2px or x2 = 2py.
- a conic section formed by the intersection of a cone by a plane parallel to its side. Standard equation: y ² = 4 ax, where 2 a is the distance between focus and directrix
