A state comprising multiple nations in which one (known as the metropolitan) dominates the others.
Example
Roman Empire: Rome was the metropolitan and gave the state its bureacracy, military hierachy, adminstration and laws. However, the peoples of the Empire comprised many different nations (such as Celts, Greeks, Egyptians, Iberians, Germans etc.) who retained their distinctive cultures, religions. The Romans recognised the nature of their empire and elected to leave these local traditions unaltered.