Ellipses
The eccentricity of an ellipse is strictly less than 1. When circles are counted as ellipses, the eccentricity of an ellipse is greater than or equal to 0; if circles are given a special category and are excluded from the category of ellipses, then the eccentricity of an ellipse is strictly greater than 0.
For any ellipse, let a be the length of its semi-major axis and b be the length of its semi-minor axis.
We define a number of related additional concepts (only for ellipses):
| name | symbol | in terms of a and b | in terms of e |
|---|---|---|---|
| first eccentricity | |||
| second eccentricity | |||
| third eccentricity | |||
| angular eccentricity |
Read more about this topic: Eccentricity (mathematics)