Polar coordinates

Any of a number of co-ordinate systems in which a point is identified by parameters identifiable as a distance from some fixed feature in space and one or more subtended angles.

Sub types include:

Circular Polar Coordinates

A two-dimensional coordinate system in which a point is located by its distance from some predefined point (known as the origin) and the angle made by a line joining from the origin to the point and some fixed axis. The angle is typically denoted θ and the distance 'r' (for radius).

Cylindrical Polar Coordinates

A three-dimenional sytem similar to circular polar coordinates except the angle and radius are measured relative a fixed straight axis in space, and a third co-ordinate is used, which measures the vertical height above some fixed plane normal to this axis.