Definition:Ellipse/Major Axis

Definition

 * EllipseParts.png

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

For convenience, let $K$ be aligned in a cartesian coordinate plane such that:
 * $F_1$ and $F_2$ are located on the X-axis
 * the midpoint of the line $F_1 F_2$ is located at the origin.

Let a straight line $M$ be drawn through $F_1$ and $F_2$ so that it intersects the perimeter of $K$ at $\left({-a, 0}\right)$ and $\left({a, 0}\right)$.

Then $M$ is the major axis of $K$.

Also see

 * Definition:Minor Axis of Ellipse