| Term | Definition |
| Deacon | an ordained man appointed by the Church to serve the poor |
| Martyr | someone who is a witness to the truth of faith by enduring death |
| Apologist | someone who defends and explains Christian beliefs |
| Atheist | someone who denies that God exists |
| Agnostic | someone who claims that God's existence cannot be known |
| bishop | an ordained Church leader("overseer") & successor of the Apostles |
| Canon | Church's complete list of books of the Bible |
| Catechumen | an unbaptized person preparing for Church membership |
| Edict of Milan | a declaration allowing religious freedom in the Roman Empire |
| Heretic | someone obstinately holding to a position contrary to official Church teaching |
| Incarnation | the truth that God(2nd person of the Trinity) assumed a human nature and became man |
| Laity | unordained baptized Catholics who continue Jesus' work on earth |
| Orthodoxy | a doctrine, attitude, or teaching that is consistent with truth and Church doctrine |
| Presbyters | another name for a priest or elder used in the early Church |
| Sacraments | effective signs of grace instituted by Jesus by which we share in the work of the Holy Spirit |
| Tradition | the living and authentic transmission of the teachings of Jesus in the Church |
| Stephen | the first Christian martyr |
| Herod Agrippa I | ruler of Palestine in the 1st century who persecuted Christians in Jerusalem |
| Nero | first Roman emperor to persecute Christians; he blamed the burning of Rome on them. |
| Constantine | first Christian Roman emperor which resulted from being victorius at the battle of the Milvian Bridge. |
| Laurence | a Roman deacon who was martyred by being roasted over hot coals. |
| Perpetua | early Christian martyr who kept a diary while in prison |
| Diocletian | emperor who divided the empire into dioceses and began the "great persecution" of christians |
| Pliny | Roman governor who wrote to Emperor Trajan seeking guidance about the problem of the Christians |
| Antioch | the first place where Jesus' followers were called Christians. |
| Felicity | a slave girl who was the companion of Perpetua |
| Tertullian | was noted for the saying, "The blood of the martyrs is the seed of the Church." |
| mysterion | In Greek, the word for sacrament referring to a person's entire life with Christ |