What is Semi-major and semi-minor axes?
[[File:Ellipse semi-major and minor axes.svg|thumb|upright=1.2|The semi-major (''a'') and semi-minor axis (''b'') of an ellipse]] In [[geometry]], the '''semi-major axis''' is the distance from the center of an [[ellipse]] to the farthest point on the perimeter of the ellipse. The semi-major axis is half of the major axis, which goes all the way across the ellipse at the widest part. The '''semi-minor axis''' is a line segment that is at [[right angle|90&nbsp;degrees]] with the semi-major axis. For the circle, the lengths of the semi-axes are both equal to the [[radius]]. {{Sci-stub}} [[Category:Orbits]]