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# ellipse

[ih-lips] /ɪˈlɪps/
noun, Geometry.
1.
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.
Origin of ellipse
1745-1755
1745-55; < French < Latin ellīpsis ellipsis; or by back formation from the plural ellipses
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2017.
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Examples from the Web for ellipse
Contemporary Examples
• A hole, though shaped like an ellipse, in which this well-hung stud had placed it would look as if a compass traced it.

• On Dec. 18, a triumphant Johnson appeared on the ellipse outside the White House to light the national Christmas tree.

March 18, 2012
Historical Examples
• If both pins were driven into the same hole, what kind of an ellipse would you get?

George C. Comstock
• The earth's orbit is an ellipse, one of the foci of which is occupied by the sun.

John Tyndall
• One pin (E) is movable along in a slot, but is adjustable at any point so that the shape of the ellipse may bep.

J. S. Zerbe
• Each one is called a focus, and an ellipse can only have one pair of foci.

Robert Stawell Ball
• The curve thus traced will be an ellipse having the pins at the two points which are called its foci.

George C. Comstock
• From the observations of the planet the ellipse in which it moves can be ascertained.

Robert Stawell Ball
• The plan of the grate of the furnace is an ellipse: fig. 73.

• The apparent path of the star is no longer a circle; it has become an ellipse.

Robert Stawell Ball
British Dictionary definitions for ellipse

## ellipse

/ɪˈlɪps/
noun
1.
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
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for ellipse
n.

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
 ellipse   (ĭ-lĭps')    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
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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
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### Difficulty index for ellipse

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### Word Value for ellipse

9
12
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