LITURGY - (Gr. a public duty or work) The work or public service of the people of God, which is the worship of the one true God. As a word liturgy means the common work or action of a particular group of people for the sake of all. Thus the divine liturgy of the Christian Church means the common work of God done by the people of God.
The Divine Liturgy is a form of public worship celebrating the Holy Eucharist. There are three forms of Liturgy: Liturgy of St. John Chrysostom which is celebrated throughout the year with the following exceptions: Liturgy of St. Basil the Great is served ten times throughout the year?five Sundays of Great Lent, Feast of St. Basil, days preceding Christmas and Theophany, Thursday and Saturday of Holy Week. Liturgy of the Presanctified Gifts is served on Wednesday and Fridays of Great Lent and the first three days of Holy Week. No Liturgy is celebrated on Good Friday ( except when the Feast of Annunciation happens to fall on that day).
Only once can the Divine Liturgy be celebrated by the same priest on the same day at the same altar on the same Antiminsion. Divine Liturgy must be celebrated before the noon hour.