The smallest radial distance of an ellipse as measured from a focus. Taking in the equation of an ellipse

gives the periapsis distance

Periapsis for an orbit around the Earth is called perigee, and periapsis for an orbit around the Sun is called perihelion.

## See also

Apoapsis,

Eccentricity,

Ellipse,

Focus
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## Cite this as:

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

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