Clergy and members of religious orders in the Middle Ages attended or celebrated Mass every day. As the summit of the Christian life, the Mass (or Divine Liturgy in the Orthodox Church) often required multiple books for the various readings, hymns, and prayers. In addition to Mass, clergy and religious orders had eight prescribed periods of prayer per day called the Divine Office: Matins, Lauds, Prime, Terce, Sext, None, Vespers, and Compline. Each period of prayer included a set of hymns, antiphons (short chanted prayers), and biblical and spiritual readings. Various types of books were used for each set of hymns and prayers until they were eventually combined into a single book called the breviary.