# diameter

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## diameter

a. a straight line connecting the centre of a geometric figure, esp a circle or sphere, with two points on the perimeter or surface
b. the length of such a line

## Diameter

The diameter of a circle is the chord that passes through the center of the circle. Moreover, the diameter of a circle is the length of this chord, equal to two radii.

In analytic geometry the diameter of a conic section (or of a curve of the second order) is understood to mean the straight line that passes through the midpoints of a set of parallel chords. For central curves of the second order (circles, ellipses, hyperbolas) this is the straight line passing through the center of the curve. In the case of the parabola, all diameters are parallel to its axis.

The concept of the diameter of a circle as the length of a segment is applied to other geometric figures and to sets of a more general nature. The diameter of a figure (or a set in metric space) is precisely the upper bound of the distances between all possible pairs of points of this figure. In this sense, the diameter of an ellipse is equal to the length of the semimajor axis, and the diameter of a square is equal to the length of its diagonal.

## diameter

[dī′am·əd·ər]
(mathematics)
A line segment which passes through the center of a circle, and whose end points lie on the circle.
The length of such a line.
For a conic, any straight line that passes through the midpoints of all the chords of the conic that are parallel to a given chord.
For a set, the smallest number that is greater than or equal to the distance between every pair of points of the set.

## diameter

The diameter of a graph is the maximum value of the minimum distance between any two nodes.

## Diameter

An authentication, authorization and accounting (AAA) protocol that replaces RADIUS (Diameter is a play on the word RADIUS). Like RADIUS, Diameter uses a challenge/response method; however, unlike RADIUS, Diameter uses the reliable TCP and SCTP protocols rather than the unreliable UDP for transport. Diameter also supports error reporting and is better at scaling than RADIUS. See RADIUS, network access server and challenge/response.
References in periodicals archive ?
1: Echographie de la vessie montrant une lesion intravesicale echogene parietale latero-superieure droite de 3 cm de diametre.
In this case only superparamagnetic clusters calculated to have diametres between 5.
D'un diametre de 325 metres, selon des observations du telescope Herschel, Apophis a ete classe parmi les asteroides "potentiellement dangereux".
Dubai The Dubai Electricity and Water Authority (Dewa) is working to increase the water flow by developing a distribution network with a 100mm to 450mm diametre.
Cementation completed work on the longest and largest diametre raise ever bored in the Canadian Shield (694 metres long by 5.
A 3,000 metre,large diametre (HQ) drill program has commenced to test these key targets.
Les vestiges de cette cite numide comprennent, notamment, des monuments megalithiques de forme circulaire, de 6 a 8 metres de diametre.
Le pot, de plus de deux metres de diametre et 1,60 m de hauteur, a ete presente devant plus de 10.
Surveille de pres par l'agence spatiale americaine, un asteroide de 45 metres de diametre a frole la Terre vendredi sans faire de degats, contrairement a une meteorite tombee le meme jour en Russie qui a explose et blesse un millier de personnes.
With a total length of 955 km of pipeline ranging from 10 to 28 inches in diametre, the planned pipeline network connecting the refineries with various terminals in the emirate of Abu Dhabi will be capable of covering the increase in demand in refined petroleum products for the foreseeable future.
The project will involve processing of one billion standard cubic feet per day of high pressure gas and transporting it from the Abu Dhabi Marine Operating Company's (Adma-Opco) offshore Umm Shaif field via a new 46 inch diametre pipeline to Adgas's integrated gas development facility on Das Island.
It could be 130 inches in diametre down to 40 inches.

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