The territorial jurisdiction of a diocesan bishop. The term also refers to the congregations and church members of the diocese. Before the church adopted the word it had a long secular usage. It was originally used in the Roman Empire for an administrative subdivision. A diocese was a division of a prefecture of the Roman Empire. In the reorganization of Diocletian and Constantine, the Roman Empire was divided into twelve dioceses. As the church expanded out from the cities, it adopted the use of the word “diocese,” and ecclesiastical dioceses tended to correspond to civil units. For example, at first the Diocese of Georgia corresponded with the State of Georgia. Later, many statewide dioceses were divided into smaller dioceses for pastoral and practical reasons.
For example, the State of New York includes six dioceses. In more recent years, some dioceses have been formed from portions of more than one state. The Diocese of the Rio Grande includes all of New Mexico and part of west Texas, and the Diocese of the Central Gulf Coast includes portions of southern Alabama and western Florida. In England, the diocese is the territory of the bishop and the parish is a subdivision of it. Every diocese in the Episcopal Church has a Standing Committee. When there is a bishop in charge of the diocese, the Standing Committee is the bishop's council of advice. When there is no bishop, bishop coadjutor or suffragan bishop, the Standing Committee is the ecclesiastical authority of the diocese. A diocese usually meets annually in a diocesan convention.
Each diocese is entitled to representation in the House of Deputies by not more than four ordained persons, presbyters or deacons, canonically resident in the diocese, and not more than four lay persons, who are confirmed adult communicants of the Episcopal Church and in good standing in the diocese. Dioceses also elect clerical and lay deputies to the Provincial Synod.
The Constitution and Canons of the Episcopal Church provide guidelines for the division of a diocese. Some persons insist that the diocese is the primary unit in the Episcopal Church.