An oval or oblong figure, bounded by a regular curve, which corresponds to an oblique projection of a circle, or an oblique section of a cone through its opposite sides. The greatest diameter of the ellipse is the major axis, and the least diameter is the minor axis. See Conic section, under Conic, and cf. Focus.
- A plane curve, especially:
- A conic section whose plane is not parallel to the axis, base, or generatrix of the intersected cone.
- The locus of points for which the sum of the distances from each point to two fixed points is equal.