Diameter

In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle.

Description

It can also be defined as the longest chord of the circle.

Both definitions are also valid for the diameter of a sphere.

The word "diameter" is derived from Greek διάμετρος (diametros), "diameter of a circle", from δια- (dia-), "across, through" + μέτρον (metron), "measure".

It is often abbreviated DIA, dia, d, or ⌀.

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 (which refers to the line itself), because all diameters of a circle or sphere have the same length, this being twice the radius r.

See also

• Angular diameter
• Caliper, micrometer, tools for measuring diameters
• Circle
• Circumference
• Conjugate diameters
• Diameter of a group, a concept in group theory
• Eratosthenes, who calculated the diameter of the Earth around 240 BC.
• Geometry
• Graph or network diameter - see Distance (graph theory)
• Hydraulic diameter
• Inside diameter
• Jung's theorem, an inequality relating the diameter to the radius of the smallest enclosing ball
• Radius
• Sauter mean diameter
• Tangent lines to circles
• Ø (disambiguation)

External links

• Diameter @ Wikipedia