n. a conic section formed by the intersection of a cone with a plane parallel with the generator; a conic with unit eccentricity, with canonical equation y² = 4ax, where 2a is the distance between focus and directrix, when the curve is symmetrical about the x-axis and has its vertex at the origin. The figure below shows a parabola with a=1. The parametric equations of a parabola are
x = at ², y = 2at.
A parabola is the projection of an arc of a circle onto an oblique plane through the chord joining the endpoints of the arc.
A parabola showing its focus and directrix.