A quantity defined for a conic section which can be given in terms of semimajor and semiminor axes .

The eccentricity can also be interpreted as the fraction of the distance along the semimajor axis at which the focus
lies,

where
is the distance from the center of the conic section
to the focus.

## See also

Circle,

Conic Section,

Eccentric Anomaly,

Ellipse,

Flattening,

Focal Parameter,

Focus,

Graph Eccentricity,

Hyperbola,

Parabola,

Semimajor Axis,

Semiminor
Axis
## Explore with Wolfram|Alpha

## Cite this as:

Weisstein, Eric W. "Eccentricity." From
*MathWorld*--A Wolfram Web Resource. https://mathworld.wolfram.com/Eccentricity.html

## Subject classifications