In 391, Theodosius I decreed that any land that had been confiscated from the church by Roman authorities be returned.
The most usual term for the geographic area of a bishop's authority and ministry, the diocese, began as part of the structure of the Roman Empire under Diocletian.
The words bishop and ordination are used in their technical meaning by the same Clement of Alexandria.
Early sources are unclear but various groups of Christian communities may have had the bishop surrounded by a group or college functioning as leaders of the local churches.
However, soon, presbyters and deacons were sent from bishop of a city church. Thus, in time, the bishop changed from being the leader of a single church confined to an urban area to being the leader of the churches of a given geographical area.
Clement of Alexandria (end of the 2nd century) writes about the ordination of a certain Zachæus as bishop by the imposition of Simon Peter Bar-Jonah's hands.
Within these churches, bishops are seen as those who possess the full priesthood and can ordain clergy – including another bishop.
Some Protestant churches including the Lutheran and Methodist churches have bishops serving similar functions as well, though not always understood to be within apostolic succession in the same way.