A relatively thin layer of material distributed in the central plane of a spiral galaxy, in contrast to the nucleus or halo.

Any of various rounded and flattened animal and plant structures.

A rotating circular plate having a magnetizable surface on which information may be stored as a pattern of polarized spots on concentric recording tracks.

See <<phonograph record>>

The region in the plane consisting of all points with norm less than 1 (sometimes less than or equal to 1).