This is a glossary of terms used in Christianity.
A
Advent – a season observed in many Western Christian churches, a time of expectant waiting and preparation for the celebration of the Nativity of Jesus at Christmas. Almah – a young woman of childbearing age. Amen – used in Jewish, Christian and Muslim worship as a concluding word or response to prayers. Ancient of Days – name for God in the Book of Daniel: Atik Yomin; in the Greek Septuagint: Palaios Hemeron; and in the Vulgate: Antiquus Dierum. Anno Domini (AD) – Latin term for Year of the Lord, the Lord in this case being Jesus, by Christian reckoning, the Messiah. Due to western dominance of the world, this has become the common world calendar system, though many cultures separately maintain their own calendars based on various events. Recently, the terms Common Era (CE) and Anno Mundi (AM) have come into use. Anointing – ritual act of pouring aromatic oil over a person's head or entire body. By extension, the term is also applied to related acts of sprinkling, dousing, or smearing a person or object with any perfumed oil, milk, butter, or other fat. Antichrist – in Christian eschatology, the Antichrist or anti-Christ is someone recognized as fulfilling the Biblical prophecies about one who will oppose Christ and substitute himself in Christ's place. Antilegomena – an epithet used by the Church Fathers to denote those books of the New Testament which, although sometimes publicly read in the churches, were not — for a considerable amount of time — considered to be genuine, or received into the canon of Scripture. They were thus contrasted with the "Homologoumena" (from Greek ομολογουμένα), or universally acknowledged writings Antinomianism – in theology, is the idea that members of a particular religious group are under no obligation to obey the laws of ethics or morality, and that salvation is by predestination only Apocalypse – any prophetic revelation or so-called End Time scenario, or to the end of the world in general Apostasy – (from Greek αποστασία, meaning a defection or revolt, from απο, apo, "away, apart", στασις, stasis, "standing") is a term generally employed to describe the formal abandonment or renunciation of one's religion, especially if the motive is deemed unworthy. In a technical sense, as used sometimes by sociologists without the pejorative connotations of the word, the term refers to renunciation and criticism of, or opposition to, one's former religion Apostle – (, apostolos, "someone sent out", e.g. with a message or as a delegate) were, according to the Synoptic Gospels and Christian tradition, disciples (followers) whom Jesus of Nazareth had chosen, named, and trained in order to send them on a specific mission. See also: Apostle (word). Apostolic Age – traditionally the period of the Twelve Apostles, dating from the Crucifixion of Jesus (c. 26–36) and the Great Commission until the death of John the Apostle Apostolic Decree – ; see Council of Jerusalem Aramaic – believed to be the primary language of Jesus. Ascension of Jesus – a Christian doctrine that says Jesus ascended to heaven in the presence of his Eleven Apostles following his resurrection, and that in heaven he sits at the right hand of God the Father Atonement – a doctrine found within both Christianity and Judaism. It describes how sin can be forgiven by God. In Judaism, Atonement is said to be the process of forgiving or pardoning a transgression. This was originally accomplished through rituals performed by a High Priest on the holiest day of the Jewish year: Yom Kippur (Day of Atonement). In Christian theology the atonement refers to the forgiving or pardoning of sin through the crucifixion of Jesus Christ which made possible the reconciliation between God and man. Within Christianity there are numerous technical theories for how such atonement might work, including the ransom theory, the Abelardian theory, the substitutionary atonement theory with its variations, and the Anselmian satisfaction theory.