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 arrangemnents. 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". 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.
What distinguishes the services found in the Euchologion is that they are generally services that have are not appointed to be done at any given time according to the Church calendar, but are done as the need arises. 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.