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[ih-lips] /ɪˈlɪps/
noun, Geometry
a plane curve such that the sums of the distances of each point in its periphery from two fixed points, the foci, are equal. It is a conic section formed by the intersection of a right circular cone by a plane that cuts the axis and the surface of the cone. Typical equation: (x 2 / a 2) + (y 2 / b 2) = 1. If a = b the ellipse is a circle.
1745-55; < French < Latin ellīpsis ellipsis; or by back formation from the plural ellipses Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for ellipse
  • The main axis of the planet's orbital ellipse shifts each time it goes round the sun.
  • If you were to cut a coelacanth across the middle, you'd see that it's almost an ellipse.
  • From that moment on, he never had any doubts about the ellipse and stated that as his first law of planetary motion.
  • He connected the whole landscape with the geometry of the circle and the ellipse.
  • The ellipse is everywhere, and essential to learning how to draw.
  • The necklace will then make an ellipse around the cone.
  • When a clause begins with as if, it must be remembered that there is an ellipse.
  • Every planet moves in an ellipse with the sun at one focus.
  • But over tens of thousands of years, the ellipse itself shifts around, so the northern summer becomes the more intense one.
  • Because the moon orbits along an egg-shaped ellipse, not a circle, its distance from us changes.
British Dictionary definitions for ellipse


a closed conic section shaped like a flattened circle and formed by an inclined plane that does not cut the base of the cone. Standard equation x²/a² + y²/b² = 1, where 2a and 2b are the lengths of the major and minor axes. Area: πab
Word Origin
C18: back formation from ellipsis
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for ellipse

1753, from French ellipse (17c.), from Latin ellipsis "ellipse," also, "a falling short, deficit," from Greek elleipsis (see ellipsis). So called because the conic section of the cutting plane makes a smaller angle with the base than does the side of the cone, hence, a "falling short." First applied by Apollonius of Perga (3c. B.C.E.).

Online Etymology Dictionary, © 2010 Douglas Harper
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ellipse in Science
A closed, symmetric curve shaped like an oval, which can be formed by intersecting a cone with a plane that is not parallel or perpendicular to the cone's base. The sum of the distances of any point on an ellipse from two fixed points (called the foci) remains constant no matter where the point is on the curve.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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ellipse in Culture
ellipse [(i-lips)]

In geometry, a curve traced out by a point that is required to move so that the sum of its distances from two fixed points (called foci) remains constant. If the foci are identical with each other, the ellipse is a circle; if the two foci are distinct from each other, the ellipse looks like a squashed or elongated circle.

Note: The orbits of the planets and of many comets are ellipses.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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