Liturgical books or texts

The Horologion (῾Ωρολόγιον; Church Slavonic: Chasoslov, Часocлoвъ), or Book of Hours, provides the fixed portions of the Daily Cycle of services (akolouthies, ἀκολουθίες) as used by the Orthodox and Eastern Catholic churches.

Into this fixed framework, numerous moveable parts of the service are inserted. These are taken from a variety of liturgical books:

• Psalter (Greek: Ψαλτήρ(ιον), "Psalter(ion)"; Slavonic: Ѱалтырь or Ѱалтирь, "Psaltyr") A book containing the 150 Psalms divided into 20 sections called Kathismata together with the nine Biblical canticles which are chanted at Matins; although these canticles had been chanted in their entirety, having over time come to be supplemented by interspersed hymns (analogously to stichera) to form the Canon, the canticles themselves are now only regularly used in a few large monasteries. The Psalter also contains the various "selected psalms", each composed of verses from a variety of psalms, sung at matins on feast days, as well as tables for determining which Kathismata are to be read at each service; in addition to the Psalms read at the daily offices, all the Psalms are read each week and, during Great Lent, twice a week.
• Octoechos (Greek: Ὀκτώηχος; Slavonic: Октоихъ, Oktoikh or Осмогласникъ, Osmoglasnik)—Literally, the Book of the "Eight Tones" or modes. This book contains a cycle of eight weeks, one for each of the eight echoi (church modes of the Byzantine musical system of eight modes), providing texts for each day of the week for Vespers, Matins, Compline, and (on Sundays) the Midnight Office. The origins of this book go back to compositions by St. John Damascene.
• Menaion (Greek: Μηναίον; Slavonic: Минїѧ, Miniya)—A twelve-volume set which provides liturgical texts for each day of the calendar year, printed as 12 volumes, one for each month of the year. Another volume, the General Menaion contains propers for each class of saints for use when the propers for a particular saint are not available. Additionally, locally venerated saints may have services in supplemental volumes, pamphlets, or manuscripts.
• Menologion A collection of the lives of the saints and commentaries on the meaning of feasts for each day of the calendar year, also printed as 12 volumes, appointed to be read at the meal in monasteries and, when there is an all-night vigil for a feast day, between Vespers and Matins.
• Triodion (Greek: Τριῴδιον, Triodion; Slavonic: Постнаѧ Трїѡдь, Postnaya Triod; Romanian: Triodul), also called the Lenten Triodion. The Lenten Triodion contains propers for:
  • the Pre-Lenten Season
  • the Forty Days of Great Lent itself
  • Lazarus Saturday and Palm Sunday
  • Holy Week

(Wikipedia)