A container for levels. A dimension contains one or more hierarchies, which in turn contain levels. For example, a single dimension might contain multiple hierarchies related to allergies. There is no formal relationship between two different hierarchies or between the levels of one hierarchy and the levels of another hierarchy. The practical purpose of a dimension is to define the default behavior of the levels that it contains — specifically the All level.

See Defining Dimensions, Hierarchies, and Levels.