This is the Orthodox liturgical book that contains the variable portions of the Liturgy and other services for a particular period of the Orthodox ecclesiastical calendar. It begins on the fourth Sunday before the Great Lent, the Sunday of the Publican and Pharisee, and ends on Saturday of the Holy Week.
Triodion is also called the period between the Sunday of the Publican and the Pharisee and Holy Pascha. The name derives from the fact that during the season the Canons contain only three odes instead of the usual nine. The canon is a series of nine hymns, ‘odes’ used at the Orthros (Matins). The nine odes vary so as to correspond with the theme of the particular feast. The introduction of canons is ascribed to St. Andrew of Crete. Other famous authors of Canons are Melodos, St. John Damascus, and St. Theodore of Studion.