Imperium
Part of speech: noun
Definition: Supreme power; dominion. The right to command the force of the state, sovereignty.
Empire
Part of speech: noun
Definition: A political unit having an extensive territory or comprising a number of territories or nations and ruled by a single supreme authority.A group of states or other territories that owe allegiance to a foreign power.A state ruled by an emperor.Any vast area under the power of one person; most commonly used in business, e.g. "the McDonalds empire".
Example sentence: Powerful indeed is the empire of habit.