| Term | Definition |
| apocalypticism | a common jewish religious perspective of Jesus' time, which held that the world had come under the control of evil forces and was heading toward the climactic End Time, at which point God would intervene to usher in a reign of perfect justice and goodness. Early Christianity was generally in keeping with apocalypticism |
| Apostle | "messenger." An early follower of Jesus' recognized as one with authority to preach the Gospel; included the 12 original disciples and Paul |
| Apostles' Creed | A short statement of Christian belief that sets forth the foundations of the central doctines of the incarnation and the Trinity; traditionally thought to have been composed by the Apostles |
| bishops | Officials within the early Church who were regarded as successors to the Apostles. They were responsible for overseeing the Church and adminstering the Eucharist |
| canon | "rule" or "standard." An autoritative set of sacred writings, such as Christianity's New Testament |
| Catholic | "universal." The largest of the three major divisions of Christianity. When it is not capitalized, the word is used generally to denote the universal nature of the Catholic Church |
| Catholic Reformation | A process begun in 1545, initiated partly by the Protestant Reformation, that clarified Church doctrines and cleaned up corrupt practices |
| Church | "assembly." The community of all Christian believers |
| deacons | "servant." Officials within the early Church who were like the presbyters in that they were on closer terms with he congregation at large |
| ecumenism | the promotion of worldwide Christian unity |
| Eucharist | Also the Lord's Supper, or Holy Communion, a central sacrament and ritual of Christianity patterned after the Last Supper, which was shared by Jesus and His twelve Apostles |
| Gospel | "good news." Referring generally to the saving power of the life, Crucifixion, and Ressurection of Jesus Christ |
| grace | God's presence freely given; a key doctrine for Paul and for Christianity |
| heresies | Sects whose theological opinions were denounced as erroneous by orthodox Christians |
| Holy Spirit | One of the three Persons of the Trinity. The New Testament describes the active presence in the ministry of Jesus, and later in the work of Jesus' followers(beginning with the Pentecost, described in chapter 2 of the Acts of the Apostles) |
| Incarnation | a core doctrine of Christianity, stating that in Jesus Christ, God became fully human while remaining fully devine |
| indulgences | reductions in our pardons of the punishment due for sins committed. The buying and selling of indulgences was a common practice in medieval Catholicism |
| martyrs | "witness." Those who choose to die rather than violate thier religious convictions |
| New Testament | a collection of twenty-seven writings that, by the late fourth century A.D. had been adopted by orthodox Christians as their primary sacred text |
| Nicene Creed | Christianty's most important creedal statement, formulated by Church leaders at the Council of Nicaea in 325 and setting forth in precise language the doctrines of the Incarnation and of the Trinity |
| original sin | Humanity's state of moral and spiritual corruption, inherited from Adam and Eve |
| orthodox | "right doctrine." The emerging version of Christianity that was deemed true by those with authority, and therefore accepted by the majority. When the word is capitalized, it refers to the major division of Christianity dominant in the eastern regions of Europe and the area surrounding the Mediterranean Sea |
| parables | stories that Jesus used to cast important moral lessons within the language and circumstances familiar to the common people |
| pope | the title conferred on the bishop of Rome, the leader of Catholicism, who is considered to be the direct successor of the Apostle Peter |
| predestination | the doctrine, especially prevalent in Calvin's form of Protestantism, stating that God has already chosen those who will be saved from sin |
| presbyters | "elder." Officials within the early Church who assisted the bishops |
| Protestant Reformation | a widespread phenomenon in sixteenth-century Europe that resulted int he emergence of Protestantism from Catholicism |
| Second Coming | the anticipated return of Christ to the world, on which occasion the dead will be resurrected and all people will be judged |
| Second Vatican Council | a worldwide council of Catholic bishops convened by Pope John XXIII, occuring from 1962 through 1965. The council aimed to update Church teaching to respond to the needs of the modern world and promote Christian unity |
| Tradition | a primary means for God's revelation of Christ, beginning with the Apostles and continuing in the present day through the Church |
| Trinity | a core Christian doctrine stating that God consists of three Persons-God the Fater, Jesus Christ the Son, and the Holy Spirit-who are at the same time one God |