O ANTIPHONS

The O Antiphons are Magnificat antiphons used at Vespers of the last seven days of Advent in various liturgical Christian traditions.

Each antiphon is a name of Christ, one of his attributes mentioned in Scripture. They are:

December 17: O Sapientia (O Wisdom)

December 18: O Adonai (O Lord)

December 19: O Radix Jesse (O Root of Jesse)

December 20: O Clavis David (O Key of David)

December 21: O Oriens (O Dayspring)

December 22: O Rex Gentium (O King of the nations)

December 23: O Emmanuel (O God is with Us)

In the Roman Catholic tradition, the O Antiphons are sung or recited at Vespers from December 17 to December 23 inclusive (but see note below on alternative English usage).
In the Church of England they have traditionally been used as antiphons to the Magnificat at Evening Prayer during this period, and although not printed in the Book of Common Prayer, have long been part of secondary Anglican liturgical sources, such as the English Hymnal. More recently they have found a place in primary liturgical documents throughout the Anglican Communion, including the Church of England's Common Worship liturgy.
Use of the O Antiphons also occurs in many Lutheran churches.
The hymn O come, O come, Emmanuel (in Latin, Veni Emmanuel) is a lyrical paraphrase of these antiphons.
The first letters of the titles taken backwards form a Latin acrostic of "Ero Cras" which translates to "Tomorrow, I will come", mirroring the theme of the antiphons.
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