Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
The major axis of a conic section is the longest diameter that passes through its center and both foci. It is commonly associated with ellipses and hyperbolas.
5 Must Know Facts For Your Next Test
In an ellipse, the major axis is the longest segment that passes through both foci.
For hyperbolas, the major axis is also called the transverse axis.
The length of the major axis in an ellipse is $2a$, where $a$ is the semi-major axis.
The endpoints of the major axis are called vertices.
For parabolas, there isn't a major axis; instead, they have an axis of symmetry.
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Related terms
Semi-Major Axis: Half of the major axis; it extends from the center to one end (vertex) of an ellipse.
Minor Axis: The shortest diameter that passes through the center and is perpendicular to the major axis in an ellipse.
Focus (Foci): Points used to define and construct conic sections; for ellipses and hyperbolas, these points lie along the major or transverse axes.