A dimension is an axis of analysis in a multidimensional structure. Typical dimensions for a sales database include time, region, department, and product.
A dimension is made of an ordered list of attributes that share a common semantic meaning in the domain being modeled. For example a Time dimension often contains attributes that allow you to analyze data by year, quarter, month, and week:
A dimension may have one or more hierarchies representing different ways of traversing the list of attributes.