# 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 ?
Tenders are invited for Boring by Reverse Type Rotary Machine of 300 mm clear inside diameter.
Clients working with pipes and tubes wanted to use stock and parts diameters.
If I hit them in soft tissue, I want a large cutting diameter for maximum damage.
In both cases, larger diameters corresponded to better scores.
Consisting of three units, the finished tool had a length of only 3,200 mm and was capable of continuous inspection of internal diameters between 16 inches and 24 inches (Figure 3).
Both the flange mounted with slit clamp supports and flange mounted with inlay slit clamp supports accommodate 8-to 30-mm shaft diameters, while dowel hole flange-mounted with slit clamp supports accommodate 12 to 30mm shaft diameters.
Where: L = length of the capillary (tube) in the die attached to the end of the barrel; and D = diameter of the capillary in the die attached to the end of the barrel.
The median diameters at which particles exhibit aerosol behavior also correspond to the sizes at which they are efficiently deposited in the lower respiratory tract when inhaled.
This means that the nominal diameter is 1/4" and that there are 20 threads per inch.
A relatively simple and inexpensive mechanical system changes pipe and calibrator diameters in 15 minutes, as compared with an hour or two for standard pipe systems.
The combined diameters of a nickel and a penny approximately equal the inside diameter of a 1-1/2-inch pipe.

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