A solid body formed when an ellipse is rotated about an axis. If it is rotated about its major axis it is a prolate ellipsoid; if it is rotated about its minor axis it is an oblate ellipsoid. For an ellipsoid centred at the origin the equation in Cartesian coordinates is:
Ellipsoid.
A quadric whose equation in a suitable coordinate system is
The three axial planes are planes of symmetry. All non‐empty plane sections of the ellipsoid are ellipses.
An ellipsoid in normal form
A body or surface in which every cross-section passing through the centre is a circle or ellipse. The Moon’s shape conforms closely to an ellipsoid with three unequal axes, the shortest being the rotation axis and the longest aligned towards the Earth. Strictly speaking, the Earth is also ellipsoidal in shape since the equator is slightly elliptical, although the difference between its longest and shortest axes is less than 1 km. See also Spheroid.
- antitail
- antithesis
- antithetic fault
- antithetic variable
- antithixotropic fluids
- antitoxin
- antitrade
- antitrades
- antitrust
- antiviral
- anti-virus program
- anti-virus software
- anti-Zeno effect
- Anti‐Comintern Pact (25 November 1936)
- Anti‐Corn Law League
- Anti‐Masonic Party
- anti‐Semitism
- Anti‐Trust laws
- Antlia
- ant lion
- Antoine equation
- Antonescu, Ion (1882–1946)
- Antoniadi, Eugène Michael
- Antoniadi, Eugène Michael (1870–1944)
- Antoniadi scale