In the history of Western world (sometimes more precisely as Greco-Roman world) adopted by the Roman Empire and the Byzantine Empire, Christian ecclesiastical provinces were named by analogy with the secular Roman province as well as certain extraterritorial formations of western world in early medieval times (see Early Middle Ages). The administrative seat of each province is an episcopal see. In hierarchical Christian churches that have dioceses, a province is a collection of those dioceses (as a basic unit of administration).