The Greek word ευχολογιον literally means "book of prayers." The Slavonic word Trebnik literally means "book of needs." This type of service book varies widely in contents and arrangements. The most comprehensive edition is the ευχολογιον το μεγα or Great Euchologion contains the prayers of the priest, deacon, and reader for Vespers, Orthros, and the Divine Liturgy; the six remaining sacraments, and other services of blessings (which in the west are often referred to as sacramentals).
The Slavonic Great Book of Needs consists of two parts:
- The sacraments and other sacred rites, which accompany a man from birth and counsels him at his departure into eternity.
- Short prayers for various needs. There is also a calendar and the "Alphabetic Classification of Names," the latter being a list of Christian names.
There are also a variety of more concise editions, that contain only the most commonly done of these services. These texts are often called the Small Euchologion (mikron euchologion), and usually contains the forms for the mysteries (sacraments) other than the Eucharist and ordination, and other common services.
The Small Book of Needs is excerpted from the Great Book of Needs for the purpose of convenience, in order to have a small book for the performance of needs, especially those needs which must be served outside the temple.
There is also a Supplemental Book of Needs in Slavonic, which contains within services such as the orders for the consecration of a temple and the consecration of things pertaining to the temple, such as the church utensils, vestments, icons, and so forth. This Supplemental Book of Needs is often combined into one book with the Small Book of Needs.
What distinguishes the services found in the Euchologion is that they are generally services that are not appointed to be done at any given time according to the Church calendar, but are done as the need arises (e.g., funerals, weddings, baptisms, the consecration of a new church, etc.). Some services are associated with the liturgical calendar, however, such as the blessing of candles on the Feast of the Presentation, the blessing of Palms on Palm Sunday, etc.
In English, there are various editions of the Small Euchologion, but only one (4 volume) edition of the entire Euchologion, published by St. Tikhon's Seminary Press under the title The Great Book of Needs.