# spheroid

A spheroid is a surface in three dimensions obtained by rotating an ellipse about one of its principal axes. If the ellipse is rotated about its major
axis, the surface is called a **prolate spheroid** (similar
to the shape of a rugby ball). If the minor axis is chosen, the surface
is called an **oblate spheroid** (similar to the shape of the
Earth). The sphere is a special case of the spheroid
in which the generating ellipse is a circle.
A spheroid is a special case of an ellipsoid where two of the three major axes are equal.