`titrebWords and Concepts of Roman Empire`/titrebThis study provides a brief review of the modes by which designation was assigned in the Roman Empire and in other ancient empires in view of the institutional and geographical vocabulary. It strives to define the concept of imperium in its legal, political, ideological and religious reality ; the term is also questioned in its ideological dimensions – as it involves both expansion and conquest –, and in its spatial aspect, distinguishing the imperium domi from the imperium militiae. Its conclusion is devoted to the Emperor as master of the Empire.