Eccentricity of a Conic Section
Ratio of the distance |PF[latex]_{1}[/latex]| between a point P of a conic section and a focus F[latex]_{1}[/latex] and the distance |PB| from the corresponding directrix.
Notation
The eccentricity of a conic section is denoted as "e", which is read "eccentricity".
In the case of an ellipse, 0 < e < 1.
In the case of a parabola, e = 1.
In the case of a hyperbola, e > 1.
In the case of a parabola, e = 1.
In the case of a hyperbola, e > 1.