| Term | Definition |
| Deacon | Office in the Church intended to serve those who are poor |
| Martyr | Means "witness" |
| Stephen | First Christian Martyr |
| Herod Agrippa I | Ruler of Palestine who persecuted Christians in Jerusalem |
| Nero | First emperor to persecute Christians |
| Constantine | First Christian Roman Emperor |
| Laurence | Roman deacon who died while being burned over hot coals |
| Perpetua | Early Christian who kept a diary in prison and died for the faith |
| Diocletian | Emperor who began dioceses and the "great persecution" of Christians |
| Pliny | Roman governor who wrote the emperor seeking guidance about what to do with Christians |
| Heretic | Someone espousing a position contrary to officially defined teachings |
| Apologist | Someone who defends and explains the faith |
| Antioch | First place that Jesus' followers were called Christians |
| Bishop | Means "overseer" |
| Presbyter | Early name for priest or elder |
| Anthony of Egypt | first known Christian monk |
| Benedict | with his sister, began monasteries in the West |
| Leo the Great | prevented the sacking of Rome |
| Nonna | converted her husband; mother of three saints |
| Arius | began a heretical movement |
| Jerome | translated the Bible into Latin |
| Monica | Augustine's mother |
| Helena | Emperor Constantine's mother |
| Augustine | wrote the first true autobiography |
| Ambrose | politician induced to become bishop of Milan |
| Monastery | place where Monks live |
| Pontifex Maximus | "greatest bridge-builder" Constantine's title |
| City of God | writing of St. Augustine/ talked about fall of Roman Empire |
| Ecumenical council | meeting of all bishops and pope that addresses Church issues |
| Apostolic See | belief that Pope follows Peter, not previous Pope |
| Fathers of the Church | faithful men who created doctrines and prayers |
| Desert fathers | Good Christian men who lived in solitude in the desert to sacrifice lives for Christ |
| Manicheism | religious group that preached a struggle between matter and spirit |
| Vulgate | Jerome's Latin translation of the bible |
| Francis of Assisi | began the Friars Minor |
| Abbot Suger | began Gothic Architecture |
| Margaret | brought about conversion of Scotland |
| William of Aquitaine and Abbot Berno | Reformed monasticism at Cluny |
| Thomas Aquinas | Medieval philosopher and theologian |
| Pope Leo III | Crowned Charlemagne Holy Roman Emperor |
| Michael Cerularius | patriarch of Constantinople |
| Hildebrand | started papal reform |
| Dominic | began the Order of Preacher |
| Clare | First member of the order of Poor Ladies |
| Cyril and Methodius | Responsible for conversion of Slavs |
| Vladimir | Responsible for conversion of Ukraine |
| Scholasticism | method of intellectual inquiry dominant in western Christian civilization. |
| Summa Theologica | St. Thomas Aquinas's Summa Theological examined Christian beliefs in light of Greek philosophy. |
| Deus vult! | God's will. Crusaders screamed this in war. |
| The First Crusade | The only successful crusade. All the others ended up being losses. |
| The Children's Crusade | a crusade where young children, some of which were not even teens, fought in battle. |
| Fathers of the Church | the early church leaders that created the teachings of the Church |
| Gregorian Reforms | reforms such as the conclave that Hildebrand or Pope Gregory VII made to improve the Church. |
| Romanesque | architecture that had thick walls, little light. |
| Ninety-Five Theses | Luther's list of complaints |
| Diet of Worms | Meeting condemning Luther |
| Cuius region, eius religio | People in a particular area are to accept the religion of their rule |
| Edict of Nantes | French Protestants given some rights |
| Sola scriptura | the bible is the only guide to truth |
| Council of Trent | Catholic reformation |
| Erasmus | Dutch humanist who remained Catholic |
| Margaret Clitherow | Executed for hiding priest |
| Thomas More | refused to acknowledge Henry VIII as head of the Church of England |
| John of the Cross | Mystic who wrote poetry |
| Charles Borromeo | One leader at the Council of Trent |
| Philip Melancthon | Lutheran Scholar |
| Philip Neri | second apostle of Rome |
| Angela Merici | educated poor girl |
| Ignatius of Loyola | Founder of Jesuits |
| Queen Elizabeth | Moved England toward Protestantism |
| John Calvin | Frenchman who emphasized predestination |
| Teresa of Avila | reformed Carmelite |
| John Knox | Introduced Presbyterianism into Scotland |
| Ulrich Zwingli | Introduced Reformation ideas into Switzerland |
| Miguel Pro | Martyred in Mexico |
| Isaac Hecker | wanted to "Americanize" Catholicism |
| Cardinal Gibbons | Baltimore's advocate for American workers |
| Saint Damien | worked with lepers in Hawaii |
| Saint Therese of Lisieux | proposed doing little things well |
| Saint Frances Cabrini | first U.S. citizen saint |
| Saint Katherine Drexel | worked with Native and African Americans |
| Thomas Merton | famous U.S. monk |
| James Walsh and Thomas Price | founded Mary knoll Missionaries |
| Virgil Michel | called for active participation in liturgy |
| Pope Pius XII | Church leader during World War II |
| Ecumenism | dialogue among religions |
| Americanism | associated with Isaac Hecker |
| Modernism | resulted in priests taking an oath against it |
| Assimilation | becoming like the dominant culture |
| Devotional catholic | Pious religious practices |