_Explanation of the Definition_.--"Prayers," this word includes not only the prayers properly so called, but also, the whole matter of the divine office. "Vocal," the Church orders the vocal recitation, the pronunciation of each word. "Established by the Church," to distinguish the official prayers of obligation from those which the faithful may choose according to their taste. "Which must be recited," for the recitation is strictly obligatory. "Daily," the Church has fixed these prayers for every day of the year, and even for certain hours of the day. "By persons deputed for that purpose," therefore, persons in holy orders recite these prayers not in their own name, but as representatives of the universal Church. _Different Names for the Breviary_.--This book which is, with us, commonly called the Breviary, has borne and still bears different names, amongst both Latins and Greeks. Amongst the Latins, the recitation of the Breviary was called the Office (_officium_), that is, the duty, the function, the office; because it is, _par excellence_, the duty, function and office of persons consecrated to God. This is the oldest and most universal name for the Breviary and its recitation. It was called, too, the Divine Office (_officium divinum_), because it has God for its principal object and is recited by persons consecrated to God. It is called the ecclesiastical office (_officium ecclesiasticum_), because it was instituted by the Church. Other names were, _Opus Dei; Agenda; Pensum servitutis; Horae; Horae Canonicae_. Which books were employed in olden times in reciting the Office? Before the eleventh century the prayers of the Divine Office were not all contained in one book, as they are now in the Breviary, which is an abridgment or compendium of several books. The recitation of the Office required the Psaltery, the Lectionary, the Book of Homilies, the Legendary, the Antiphonarium, the Hymnal, the Book of Collects, the Martyrology, the Rubrics. The Psaltery contained the psalms; the Lectionary (thirteenth century) contained the lessons of the first and second nocturn; the Book of Homilies, the homilies of the Fathers; the Legendary (before the thirteenth century), the lives of the saints read on their feast days. The Hymnal contained hymns; the Book of Collects, prayers, collects and chapters; the Martyrology contained the names with brief lives of the martyrs; the Rubrics, the rules to be followed in the recitation of the Office. To-day, we have traces of this ancient custom in our different choir books, the Psalter, the Gradual, the Antiphonarium. There were not standard editions of these old books, and great diversities of use and text were in existence.