Τριῴδιον/Triōdion; Slavonic: Постнаѧ Трїωдь/Postnaya Triod) is an Orthodox
Christian Liturgical term, referring both to the 70-day period preceding
Páscha as well as to the service book providing the texts for the Divine
Services during this period.
Oktoechos Troparia for Friday evening Vespers, Saturday morning Matins, and Sunday
evening Vespers in the eight Tones.
For other materials, refer to the complete Októechos.