A small circle whose centre rolls around the circumference of a larger fixed circle. The curve traced out by a point on the epicycle is called an epicycloid.
In the Ptolemaic system of planetary motion, a hypothetical small circle whose centre moved along the circumference of a bigger circle, the deferent (see diagram). Combinations of epicycles could be used to reproduce the observed motions of the planets, without abandoning the Greek dogma that only circular motions were allowable in the heavens.
- Andean orogenic belt
- Anderson bridge
- Anderson, Carl David
- Anderson, Carl David (1905–91)
- Anderson, Clayton Conrad (1959– )
- Anderson, Elizabeth Garrett (1836–1917)
- Anderson, John (1893–1962)
- Anderson localization
- Anderson, Michael Philip (1959–2003)
- Anderson, Philip Warren
- Anderson, Philip Warren (1923–2020)
- Anderson, Theodore Wilbur (1918–2016)
- Andersonville Prison
- Anderson–Darling test
- Anders, William Alison (1933– )
- andesine
- andesite
- AND gate
- andhis
- andic horizon
- Andino-type margin
- andisols
- AND operation
- AND/OR graph
- Andorra