The O Antiphons are antiphons used at daily prayer in the evenings of the last days of Advent, from December 17 to December 23. 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 Adonai)
- December 19: O Radix Jesse (O Root of Jesse)
- December 20: O Clavis David (O Key of David)
- December 21: O Oriens (O Morning Star)
- December 22: O Rex Gentium (O King of the nations)
- December 23: O Emmanuel (O Emmanuel)
The hymn O come, O come, Emmanuel is based on these antiphons.
The first letters of the titles taken backwards form the Latin phrase "Ero Cras" which means "Tomorrow, I will come" which points the the season of Advent as a time of preparation for Christ’s coming.
