The ministerial orders of the Catholic Church include the orders of bishops, deacons and presbyters, which in Latin is sacerdos. The ordained priesthood and common priesthood (or priesthood of the all the baptized) are different in function and essence.
A distinction is to be made between "priest" and "presbyter." In the 1983 Code of Canon Law, "The Latin words sacerdos and sacerdotium are used to refer in general to the ministerial priesthood shared by bishops and presbyters. The words presbyter, presbyterium and presbyteratus refer to priests [in the English use of the word] and presbyters".
The priesthood in the Catholic Church includes the priests of both the Latin Rite and the Eastern Rites. As of May 2007, the
Vatican website stated that there were some 406,411 priests serving the Church worldwide. While the consecrated life is neither clerical nor lay by definition, clerics can be members of institutes of consecrated, or secular (diocesan), life.
The Priesthood is understood to have begun with the Last Supper, when Jesus Christ instituted the Eucharist. While the threefold ministry is recorded in the New Testament, it is believed that in many assemblies this complete articulation did not take place until the second century. Until then, most small communities were led by an episkopos (overseer or bishop) or a presbyteros(elder or priest), hence in Catholic theology they are referred to as presbyter-bishops in this period. As communities grew in size and needed more ministers, the bishops became the highest level of minister in the Church with priests assisting them in presiding at the Eucharist in the multiple communities in each city. The diaconate (deacon means 'servant') evolved as administrators of Church funds and programmes for the poor.
Theology of the priesthood
Passover and Christ
The theology of the Catholic priesthood is rooted in the priesthood of Christ and to some degree shares elements of the ancient Hebraic priesthood as well. A priest is one who presides over a sacrifice and offers that sacrifice and prayers to God on behalf of believers. The ancient Jewish priesthood which functioned at the temple in
offered animal sacrifices at various times throughout the year for a variety of reasons. Jerusalem
In Christian theology, Jesus is the Lamb provided by God himself as a sacrifice for the sins of the world. Before his death on the cross, Jesus celebrated the Passover with his disciples and offered blessings over the bread (matzoh) and wine respectively, saying: "Take and eat. This is my body” and "Drink from this all of you, for this is my blood, the blood of the covenant, poured out for the forgiveness of sins." (Matthew 26:26b-28
Bible). The next day Christ's body and blood became visible in his sacrifice on the cross. Catholics believe that it is this same body, sacrificed on the cross and risen on the third day which is made present in the offering of each Eucharistic sacrifice which is called the Eucharist. However, Catholicism does not believe that the essence of the real presence of Christ in the Eucharist entails that the accidental features also change. For example, scientific analysis of the Eucharistic elements would indicate the physical properties of wine and unleavened bread (or leavened bread in the case of Eastern Rite Catholics). Jerusalem
Thus priests (and bishops who are “high priests”) in presiding at the Eucharist join each offering of the Eucharistic elements in union with the sacrifice of Christ. Catholic ordained ministers are known as priests because by their celebration of the Eucharist, they offer in a new moment in time the one eternal sacrifice of Christ.
Catholicism does not teach that Christ is sacrificed again and again, but that "The sacrifice of Christ and the sacrifice of the Eucharist are one single sacrifice.". Instead, the Catholic Church holds the Jewish concept of memorial in which "..the memorial is not merely a recollection of past events....these events become in a certain way present and real." and thus "...the sacrifice Christ offered once and for all on the cross remains ever present." Properly speaking, in Catholic theology, expressed by Saint Thomas Aquinas, "Only Christ is the true priest, the others being only his ministers." Thus, Catholic clergy share in the one, unique, Priesthood of Christ.