Pa*rab"o*la (?), n.; pl. Parabolas (#). [NL., fr. Gr. &?;; -- so called because its axis is parallel to the side of the cone. See Parable, and cf. Parabole.] (Geom.) (a) A kind of curve; one of the conic sections formed by the intersection of the surface of a cone with a plane parallel to one of its sides. It is a curve, any point of which is equally distant from a fixed point, called the focus, and a fixed straight line, called the directrix. See Focus. (b) One of a group of curves defined by the equation y = axⁿ where n is a positive whole number or a positive fraction. For the cubical parabola n = 3; for the semicubical parabola n = &frac32;. See under Cubical, and Semicubical. The parabolas have infinite branches, but no rectilineal asymptotes.

• (mathematics) The conic section formed by the intersection of a cone with a plane parallel to a tangent plane to the cone; the locus of a point equidistant from a point (the focus) and a line (the directrix).