Semimajor axis (original) (raw)

In an elliptical shape, the major axis is the longest line that runs through the center of the ellipse, its ends being at the widest points of the shape. The semimajor axis is one half of the major axis; running from the center, through a focus, and to the edge of the ellipse.

For a more in-depth explanation, see ellipse. Also contrast with semiminor axis.