
eccentricity


A measure of a conic section (circle, ellipse, parabola, or hyperbola), defined as the ratio of the distance of any point on the curve from the focus to the distance of that point from the directrix (a fixed line).
A circle has an eccentricity of zero; an ellipse has an eccentricity of less than one; a parabola has an eccentricity of one; and a hyperbola has an eccentricity of greater than one.

