All divine services in Orthodox churches are conducted according to special books, which contain the sequence of festive services, as well as those of the Mother of God, saints and angels. We can talk about some of the main books, without which the performance of Orthodox divine services will be impossible.
Among the main liturgical books are the octoi, the monthly menaion, the festive menaion, the general menaion, the lenten triode and the colored triode.
Octoechos is a liturgical book in which a service is scheduled for each day of the week for eight voices (church tunes). Otherwise, the octoi are called the octopus. Compiled by the Monk John of Damascus in the VIII century. The book is divided into two parts. In the first there are services of the 1st - 4th voices, in the second 5th - 8th voices. Octoich is used almost all the time of the calendar year, except for some special holidays.
The monthly Menaion book contains services to the saints, the Mother of God, angels, as well as the main Lord's feasts. There are several dozen volumes of the monthly Menaion, since this book describes services for each day of the entire calendar year. In the festive Menaion there are only festive services to the Lord, the Mother of God, angels and some revered saints. In the general minea, there are general liturgical texts according to the ranks of the saints, as well as a general service to the Mother of God and the Lord.
The Lenten Triodion is used during the preparatory weeks for holy Great Lent, as well as during Great Lent itself. It contains the services of Lenten and Holy Week. In the colored Triode, services can be found from Easter to All Saints' Sunday (the next Sunday after Trinity).
In addition, there are the liturgical Gospels and the Apostle. From them passages of sacred texts are read during the service.
Among other liturgical books, one can also highlight the book of hours (used by psalmists to read the hours, there is also the sequence of the main daily divine services) and irmology (contains selected hymns of the canons, irmos, selected psalms).
