Noun
Triodion (plural Triodions or Triodia)
(Christianity) The liturgical book used by the Eastern Orthodox Church, containing the propers for the fasting period preceding Easter and for the weeks leading up to the fast.
Regardless of the rank of the feast being celebrated, the Lenten hymns contained in the Triodion are never omitted, but are always chanted in their entirety, even on the feast of the Annunciation. Source: Internet
The Sunday of the Publican and the Pharisee is the first day the Lenten Triodion is used (at Vespers or All-Night Vigil on Saturday night), though it is only used for the Sunday services, with nothing pertaining to weekdays or Saturday. Source: Internet
The Triodion begins during the Pre-Lenten period to supplement or replace portions of the regular services. Source: Internet
This theme of "Lenten joy" is also found in many of the hymns of the Triodion, such as the stichera which begin with the words: "The Lenten Spring has dawned!.. Source: Internet
Though there are no materials provided in the Lenten Triodion for this day, it is the very first day that is affected by the date of the upcoming Pascha (all the preceding days having been affected by the previous Pascha). Source: Internet