Apolytikion
The Apolytikion or Dismissal Hymn is a troparion said or sung at Orthodox Christian worship services. The apolytikion summarizes the feast being celebrated that day. It is chanted at Vespers, Matins and the Divine Liturgy; and it is read at each of the Little Hours. The name derives from the fact that it is chanted for the first time before the dismissal of the first service of the liturgical day, Vespers, the liturgical day beginning at sunset in the Orthodox Church.
Although the term apolytikion is used in the Greek language, there is no equivalent word in Church Slavonic where variously are used such terms as "отпустительный тропарь", "тропарь праздника", "тропарь святого", and so on.
Examples
The apolytikion of the Feast of the Nativity :Your birth, O Christ our God, dawned the light of knowledge upon the earth. For by Your birth those who adored stars were taught by a star to worship You, the Sun of Justice, and to know You, Orient from on High. O Lord, glory to You.
The apolytikion for the Feast of the Annunciation :
Today is the crowning of our salvation and the manifestation of the Mystery which is from eternity; the Son of God becometh the Son of the Virgin, and Gabriel announceth the glad tidings of grace: wherefore let us cry out with him to the Mother of God; Hail, full of grace, the Lord is with thee!
The apolytikion of Pascha :
Christ is risen from the dead, trampling down death by death, and upon those in the tombs bestowing life!
There are also eight Resurrectional Apolytikia for the Lord's Day, Sunday written in each of the Eight Tones.