A book containing the daily public or canonical prayers of the Roman Catholic or of the Greek Church for the seven canonical hours, namely, matins and lauds, the first, third, sixth, and ninth hours, vespers, and compline; -- distinguished from the missal.
A service book containing the texts necessary for the celebration of the Divine Office. From the 11th century on, the various volumes used during the Divine Office (Psalter, Antiphonal, Lectionary, Collectar, Martyrology, and others) were combined to form the breviary. All members of the monastic orders and the clergy in major orders are committed to the daily recitation of the breviary.
The book containing the Liturgy of the Hours* or "Divine Office" which every priest and brother is obliged to recite each day.