- 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
n.1570s, from Modern Latin parabola, from Greek parabole “parabola, comparison, analogy; application” (see parable), so called by Apollonius of Perga c.210 B.C.E. because it is produced by “application” of a given area to a given straight line. It had a different sense in Pythagorean geometry. Related: Parabolic.
- The curve formed by the set of points in a plane that are all equally distant from both a given line (called the directrix) and a given point (called the focus) that is not on the line.
A geometrical shape (see geometry) consisting of a single bend and two lines going off to an infinite distance.