Sentence:  These ministers were at first confined to the three orders of <WSD>bishops</WSD>, priests, and deacons. 
Meaning of the word marked with <WSD> tags:  An overseer of congregations: either any such overseer, generally speaking, or (in Eastern Orthodoxy, Catholicism, Anglicanism, etc.) an official in the church hierarchy (actively or nominally) governing a diocese, supervising the church's priests, deacons, and property in its territory.