A cathedra is the raised throne of a bishop in the early Christian basilica. When used with this meaning, it may also be called the bishop's throne. With time, the related term cathedral became synonymous with the "seat", or principal church, of a bishopric. The word in modern languages derives from a normal Greek word καθέδρα [kathédra], meaning "seat", with no special religious connotations, and the Latin cathedra, specifically a chair with arms. It is a symbol of the bishop's teaching authority in the Catholic Church, the Orthodox Church, and the Anglican Communion churches. Etymology The English word "cathedra", plural cathedrae, comes from the Latin word for "armchair", itself derived from the Greek. After the 4th century, the term's Roman connotations of authority reserved for the Emperor were adopted by bishops. It is closely related to the etymology of the word chair. Cathedrae apostolorum The term appears in early Christian literature in the phrase cathedrae apostolorum, indicating authority derived directly from the apostles. Ex cathedra The doctrine of papal infallibility, the Latin phrase ex cathedra (literally, "from the chair") was proclaimed at the First Vatican Council by Pius IX in 1870 as meaning "when, in the exercise of his office as shepherd and teacher of all Christians, in virtue of his supreme apostolic authority, the Bishop of Rome defines a doctrine concerning faith or morals to be held by the whole Church." Cathedra as bishop's see Tertullian (c. 155 – c. 240?) was the first to use cathedra in the meaning of a bishop's see. Cathedrals as a bishop's seat Eventually, the main church of a diocese, used as the primary church by its bishop, received the title 'cathedral'. The cathedral is literally the church into which a bishop's official cathedra is installed. The Joint International Commission for Theological Dialogue Between the Catholic Church and the Orthodox Church makes use of the term cathedral to point out the existence of a bishop in each local church, in the heart of ecclesial apostolicity. Notable examples Cathedra Petri The definitive example of a cathedra is that encased within the Triumph of the cathedra Petri designed by Gian Lorenzo Bernini in 1657, and completed and installed in St Peter's Rome in 1666. As early as the 8th century, an ancient wooden chair overlaid with ivory plaques depicting The Twelve Labours of Heracles and some of the constellations, was venerated as the episcopal chair