What is "pentecostarion"

The Pentecostarion ( Greek: Πεντηκοστάριον, Pentekostárion; Slavonic: Цвѣтнаѧ Трїωдь, ''Tsvyetnaya Triod' '', literally "Flowery Triodon"; ) is the liturgical book used by the Eastern Orthodox and Eastern Catholic Churches which follow the Byzantine Rite during the Paschal Season which extends from Pascha (Easter) to the Sunday following All Saints Sunday (i.e., the Second Sunday After Pentecost).

The name means the Book of the "Fifty Days", referring to the period of time from Pascha to Pentecost. In Greek, it is also sometimes called the Joyful Pentecostarion (Πεντηκοστάριον χαρμόσυνον, Pentekostárion Charmósynon). In English, it is sometimes called the Paschal Triodion. The name "Pentecostarion" is also applied to the liturgical season covered by the book.

The Pentecostarion is part of the Paschal cycle or "Moveable Cycle" of the ecclesiastical year. This cycle is dependent upon the date of Pascha and continued throughout the coming year until the next Pascha.

Pascha (Easter) is the most important feast of the entire year, outranking by far all others. Each week of the Pentecostarion is named after the Gospel lesson which is read on the Sunday which begins it; for instance, the week that follows Thomas Sunday is referred to as Thomas Week. During the liturgical season of the Pentecostarion, the Gospel of John is read in full, as is the Acts of the Apostles. Both of these books were chosen because of their instructive content. Pascha (Easter) is the traditional time for baptizing new converts to the faith. So, just as Great Lent, with its liturgical book, the Triodion, was the final period of preparation for the catechumens before their baptism, so the time of the Pentecostarion is the time of initiation into the Sacred Mysteries of the Christian religion for the "Newly Illumined" (i.e., the newly baptized).

The two Sacred Mysteries of baptism and chrismation are reflected in the two feasts which mark the beginning and ending points of the Pentecostarion: Pascha and Pentecost. Baptism is naturally tied to the Resurrection, according to the Apostle Paul (, , ). Chrismation, the reception of the Gifts of the Holy Spirit is naturally reflected in Pentecost. Because of this, the imagery of water figures prominently in the hymns of the Pentecostarion.

The services of the Pentecostarion begin during the Paschal Vigil starting at the stroke of midnight on Easter Sunday. The service for Pascha is radically different from the services of any other time of the year. Throughout the course of the Pentecostarion, they gradually return to normal (see Canonical hours and Divine Liturgy).