In geometry, a

**disk**is an n-dimensional region bounded by an (n-1) dimensional hypersphere. A disk is said to be closed or open according to whether the region does or does not include its boundary. A

**ball**is a disk in a space with > 2 dimensions.

A **representative disk** is three-dimensional volume element of a solid of revolution. The element is created by rotating a line segment (of length "*w*") around some axis (located "*r*" units away); such that, a cylindrical volume, of *π*∫*r*^{2}*w* units, is enclosed.

In topology, a

**open disk**and a

**closed disk**in a metric space are the same as open ball and closed ball. In particle, in a two dimensional Euclidean space, an open (closed) disk is an circular area without (with) its boundary circle.

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