The distance across a circle or sphere, measured with a straight line passing through the center. It's the furthest away two points on the circle or sphere can be from each other.

Twice the radius.

In combinatorics, the diameter is the maximum distance between any two points in a set.

--back to combinatorics--

Di*am"e*ter (?), n. [F. diametre, L. diametros, fr. Gr. ; through + measure. See Meter.]

1. Geom. (a)

Any right line passing through the center of a figure or body, as a circle, conic section, sphere, cube, etc., and terminated by the opposite boundaries; a straight line which bisects a system of parallel chords drawn in a curve.

(b)

A diametral plane.

2.

The length of a straight line through the center of an object from side to side; width; thickness; as, the diameter of a tree or rock.

In an elongated object the diameter is usually taken at right angles to the longer axis.

3. Arch.

The distance through the lower part of the shaft of a column, used as a standard measure for all parts of the order. See Module.

Conjugate diameters. See under Conjugate.

Log in or register to write something here or to contact authors.