Definition:Ellipse/Minor Axis

Definition

Consider an ellipse $K$ whose foci are $F_1$ and $F_2$.

Definition $1$

The minor axis of $K$ is the line segment through the center of $K$ perpendicular to the major axis of $K$ such that its endpoints are the points of intersection with $K$.

Definition $2$

The minor axis of $K$ is the diameter of $K$ which has the smallest length.

In the above diagram, $C_1 C_2$ is the minor axis of $K$.

Semi-Minor Axis

A semi-minor axis of $K$ is either half of the minor axis of $K$ from its midpoint to its endpoint.

Also see

• Equivalence of Definitions of Minor Axis of Ellipse
• Minor Axis of Ellipse is Axis of Symmetry
• Definition:Major Axis of Ellipse

• Results about the minor axis of an ellipse can be found here.

Linguistic Note

The plural of axis is axes, which is pronounced ax-eez not ax-iz.

Compare basis.