Bishop, Priest, Deacon
THE sacrament of holy orders is conferred in three ranks of clergy: bishops, priests, and deacons.
Bishops (episcopoi) are those who have care of multiple congregations and have the task of appointing, ordaining, and disciplining priests and deacons. They are often called 'evangelists' in the New Testament. Examples of first century bishops include Timothy and Titus (1 Tim. 5:19-22, 2 Tim. 4:5, Titus 1:5).
Priests (presbuteroi) are also known as "presbyters" or "elders." In fact, the English term "priest" is simply a contraction of the Greek word "presbuteros." They have the responsibility of teaching, governing, and performing the sacraments in a given congregation (1 Tim. 5:17, Jas. 5:14-15).
Deacons (diakonoi) are the assistants of the bishops and have the task of teaching and administering certain church functions, such as the distribution of food (Acts 6:1-6).
In the apostolic age, the terms for these offices were still some what fluid. Sometimes a term would be used in a technical sense as the title for an office, sometimes not. This technical versus non-technical use of the terms even exists today, as when a Protestant pastor who is actually an ordained elder is also called a "minister" (Gk., diakonos), though he is not a member of his congregation's deacon board.
Thus in the apostolic age Paul sometimes describe himself as a diakonos ("servant" or "minister"; cf. 2 Cor. 3:6, 6:4, 11:23, Eph. 3:7) even though he had an office much higher than that of a deacon, being as he was an apostle.
Similarly, on one occasion Peter described himself as a "fellow elder" even though he, being an apostle, also had a much higher office than that of an ordinary elder.
The term for bishop, episcopos ("overseer"), was also fluid in meaning. Sometimes it designated those who were overseers of an individual congregation (the priests), sometimes the person who was the overseer of all the congregations in a city or area (the bishop or evangelist), and sometimes simply the highest ranking clergyman in the local church--a person who could be an apostle if one were staying there at the time.
Although the terms bishop, priest, and deacon were somewhat fluid in the apostolic age, by the beginning of the second century they had achieved the fixed form in which they are used today to designate the three offices, whose functions are clearly distinct in the New Testament.