An
oblate spheroid is a
rotationally symmetric ellipsoid having a polar axis shorter than the diameter of the equatorial circle whose plane bisects it. An
M&M's candy (plain) (US) or
Smartie (Canada, UK and Europe) is an approximate example of an oblate spheroid.
It can be formed by rotating an ellipse about its minor axis, forming an equator with the end points of the major axis. As with all ellipsoids, it can also be described by the lengths of three mutually perpendicular principal axes, which are in this case two arbitrary equatorial semi-major axes and one semi-minor axis.
The opposite of oblate is prolate.
The aspect ratio, ba, is the ratio of the polar to equatorial lengths[citation needed], while the flattening (also called oblateness), f, is the ratio of the equatorial-polar length difference to the equatorial length
