An -D disk (or Disc) of Radius is the collection of points of distance (Closed Disk) or (Open Disk) from a fixed point in Euclidean -space. A disk is the Shadow of a Ball on a Plane Perpendicular to the Ball-Radiant Point line.

The -disk for is called a Ball, and the boundary of the -disk is a -Hypersphere. The standard -disk, denoted (or ), has its center at the Origin and has Radius .

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1999-05-24