An ellipse is a kind of oval. It is the oval formed by the intersection of a plane and a right circular cone-one of the four types of conic sections. The other three are the circle, the hyperbola, and the parabola. The ellipse is symmetrical along two lines, called axes. The major axis runs through the longest part of the ellipse and its center, and the minor axis is perpendicular to the major axis through the ellipse's center.

Other definitions of an ellipse

Ellipses are described in several ways, each way having its own advantages and limitations:

1. The set of points, the sum of whose distances from two fixed points (the foci, which lie on the major axis) is constant. That is, P: PF₁ + PF₂ = constant.

2. The set of points whose distances from a fixed point (the focus) and fixed line (the directrix) are in a constant ratio...