Diameter

Diameter is a term used in geometry to describe a straight line passing from side to side through the center of a body or figure, especially a circle or sphere.

Definition

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. The diameters are the longest chords of the circle. The diameter of a circle is twice its radius.

Applications

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 or sphere have the same length, this being twice the radius. For a convex shape in the plane, the diameter is defined to be the largest distance that can be formed between two opposite points.

Related Terms

• Radius: The radius of a circle is the distance from the center of the circle to any point on its circumference. The radius is half the diameter.
• Circumference: The circumference of a circle is the distance around it. The circumference is π times the diameter.
• Chord: A chord of a circle is a straight line segment whose endpoints both lie on the circle. A diameter is the longest possible chord of a circle.

See Also

• Geometry
• Circle
• Sphere

Diameter Resources
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