# Ellipse

- Sum of the distance from two special points inside the ellipse to any point is always the same
- The two points are called its
**foci** - Widest diameter is its
**major axis** - The distance from the center to one end is the
**semi-major axis**

## Eccentricity

- Roundness is determined by how close the foci are
- How "squashed" an ellipse is
- A circle has an eccentricity of 0