semimajor axis
geometry
Quick Summary
The semimajor axis is half of the major axis of an ellipse. The major axis is a straight line drawn through the foci of an ellipse and extended to the curve in either direction. The semimajor axis is a key component in describing the geometry of an ellipse, which is a closed curve defined by specific mathematical properties. For instance, in astronomy, the orbits of planets around the Sun are elliptical, and the semimajor axis is used to define the size and shape of these orbits.12
Summary created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
3 Britannica Sources
Ask Britannica AI about this topic
Britannica doesn't have a full article on this topic, so we've curated a list of our relevant coverage.
