A diocese, from the Greek term ''διοίκησις'', meaning "administration", is the district under the supervision of a bishop. A diocese is divided into parishes (in the Church of England into benefices and parishes). This structure of church governance is known as episcopal polity. The word diocesan means relating or pertaining to a diocese. It can also be used as a noun meaning the bishop who has the principal supervision of a diocese.
In the Latter Day Saint movement, the term "bishopric" is used to describe the bishop himself, together with his two counselors, not the ward or congregation of which a bishop has charge.
An archdiocese (or archiepiscopal see or archbishopric) is more significant than a diocese. An archdiocese is presided over by an archbishop whose see may have or have had importance due to size or historical significance. The archbishop may have metropolitan authority over any other suffragan bishops and their dioceses within his ecclesiastical province.
A diocese also may be referred to as a ''bishopric'' or ''episcopal see'', though strictly the term ''episcopal see'' refers to the domain of ecclesiastical authority officially held by the bishop, and the term ''bishopric'' to the post of being bishop.
Especially in the Middle Ages, some bishops (e.g. prince-bishops) held political as well as religious authority within their dioceses, which in practice were thus also independent or semi-independent states.
== History ==
In the later organization of the Roman Empire, the increasingly subdivided provinces were administratively associated in a larger unit, the diocese (Latin ''dioecesis'', from the Greek term ''διοίκησις'', meaning "administration").
With the adoption of Christianity as the Empire's official religion in the 4th century, the clergy assumed official positions of authority alongside the civil governors. A formal church hierarchy was set up, parallel to the civil administration, whose areas of responsibility often coincided.
With the collapse of the Western Empire in the 5th century, the bishops in Western Europe assumed a large part of the role of the former Roman governors. A similar, though less pronounced, development occurred in the East, where the Roman administrative apparatus was largely retained by the Byzantine Empire. In modern times, many dioceses, though later subdivided, have preserved the boundaries of a long-vanished Roman administrative division. For Gaul, Bruce Eagles has observed that "it has long been an academic commonplace in France that the medieval dioceses, and their constituent ''pagi'', were the direct territorial successors of the Roman ''civitates''.〔, noting for instance 〕
Modern usage of 'diocese' tends to refer to the sphere of a bishop's jurisdiction. This became commonplace during the self-conscious "classicizing" structural evolution of the Carolingian Empire in the 9th century, but this usage had itself been evolving from the much earlier ''parochia'' ("parish"), dating from the increasingly formalised Christian authority structure in the 4th century.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』