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From Nordan Symposia
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==Etymology==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] diametre, from Middle French, from [[Latin]] diametros, from [[Greek]], from dia- + metron [[measure]]
*Date: [http://www.wikipedia.org/wiki/14th_Century 14th century]
==Definitions==
*1 : a chord passing through the [[center]] of a figure or [[body]]
*2 : the length of a straight line through the [[center]] of an object
*3 : a [[unit]] of enlargement used with a [[number]] to indicate magnification by a lens or optical system <an object one millimeter wide magnified 40 diameters appears 40 millimeters wide>
==Description==
In geometry, a '''diameter''' of a [[circle]] is any straight [http://en.wikipedia.org/wiki/Line_segment line segment] that passes through the [[center]] of the [[circle]] and whose endpoints are on the [[circle]]. The diameters are the longest [http://en.wikipedia.org/wiki/Chord_(geometry) chords] of the circle. The [[word]] "diameter" derives from [[Greek]] διάμετρος (diametros), "diagonal of a circle", from δια- (dia-), "across, through" + μέτρον (metron), "a [[measure]]".
In more modern usage, the length of a diameter is also called the diameter. In this sense one speaks of the diameter rather than a diameter, because all diameters of a circle have the same length, this being twice the [[radius]].
For a [http://en.wikipedia.org/wiki/Convex_set convex shape] in the plane, the diameter is defined to be the largest distance that can be formed between two opposite [[parallel]] lines tangent to its [[boundary]], and the width is defined to be the smallest such distance. For a [http://en.wikipedia.org/wiki/Curve_of_constant_width curve of constant width] such as the [http://en.wikipedia.org/wiki/Reuleaux_triangle Reuleaux triangle], the width and diameter are the same because all such pairs of [[parallel]] [[tangent]] lines have the same distance. [http://en.wikipedia.org/wiki/Diameter]
[[Category: Mathematics]]
==Etymology==
[http://nordan.daynal.org/wiki/index.php?title=English#ca._1100-1500_.09THE_MIDDLE_ENGLISH_PERIOD Middle English] diametre, from Middle French, from [[Latin]] diametros, from [[Greek]], from dia- + metron [[measure]]
*Date: [http://www.wikipedia.org/wiki/14th_Century 14th century]
==Definitions==
*1 : a chord passing through the [[center]] of a figure or [[body]]
*2 : the length of a straight line through the [[center]] of an object
*3 : a [[unit]] of enlargement used with a [[number]] to indicate magnification by a lens or optical system <an object one millimeter wide magnified 40 diameters appears 40 millimeters wide>
==Description==
In geometry, a '''diameter''' of a [[circle]] is any straight [http://en.wikipedia.org/wiki/Line_segment line segment] that passes through the [[center]] of the [[circle]] and whose endpoints are on the [[circle]]. The diameters are the longest [http://en.wikipedia.org/wiki/Chord_(geometry) chords] of the circle. The [[word]] "diameter" derives from [[Greek]] διάμετρος (diametros), "diagonal of a circle", from δια- (dia-), "across, through" + μέτρον (metron), "a [[measure]]".
In more modern usage, the length of a diameter is also called the diameter. In this sense one speaks of the diameter rather than a diameter, because all diameters of a circle have the same length, this being twice the [[radius]].
For a [http://en.wikipedia.org/wiki/Convex_set convex shape] in the plane, the diameter is defined to be the largest distance that can be formed between two opposite [[parallel]] lines tangent to its [[boundary]], and the width is defined to be the smallest such distance. For a [http://en.wikipedia.org/wiki/Curve_of_constant_width curve of constant width] such as the [http://en.wikipedia.org/wiki/Reuleaux_triangle Reuleaux triangle], the width and diameter are the same because all such pairs of [[parallel]] [[tangent]] lines have the same distance. [http://en.wikipedia.org/wiki/Diameter]
[[Category: Mathematics]]
