The “O Antiphons” refer to the seven antiphons that are recited (or chanted) preceding the Magnificat during Vespers of the Liturgy of the Hours. They cover the special period of Advent preparation known as the Octave before Christmas, Dec. 17-23, with Dec. 24 being Christmas Eve and Vespers for that evening being for the Christmas Vigil.
"The O Antiphons are the seven jewels of our liturgy, dating back to the fourth century, one for each day until Christmas Eve. These antiphons address Christ with seven magnificent Messianic titles, based on the Old Testament prophecies and types of Christ. The Church recalls the variety of the ills of man before the coming of the Redeemer."
The "O" Antiphons are the verses for the ancient hymn O Come, O Come Emmanuel. The first letter of the Messianic titles: Emmanuel, Rex, Oriens, Clavis, Radix, Adonai, Sapientia—spell out Latin words ERO CRAS, meaning, "Tomorrow, I will come."
The antiphons are part of the evening prayer of the Divine Office, the antiphon before and after the Magnificat. They are also the alleluia verse before the Gospel at Mass.
December 17th: O Wisdom, you come forth from the mouth of the Most High. You fill the universe and hold all things together in a strong yet gentle manner. O come to teach us the way of truth.
Since the symbol for wisdom is a book, you could give each child a new book.
December 18th: O Lord and leader of Israel, you appeared to Moses in a burning bush and you gave him the Law on Sinai. O come and save us with your mighty power.
Tonight, you could have a bon fire and make smores.
December 19th: O flower of Jesse, you stand as a signal for the nations; kings fall silent before you whom the peoples acclaim. O come to deliver us, and do not delay.
Today you could decorate the house with poinsettias.
December 20th: O key of David and scepter of Israel, what you open no one else can close again; what you close no one can open. O come to lead the captive from prison; free those who sit in darkness and in the shadow of death.
December 21st: O Radiant Dawn, you are the splendor of eternal light and the sun of justice. O come and enlighten those who sit in darkness and in the shadow of death.
Tonight you could go for a walk or drive around to view the Christmas lights.
December 22nd: O King whom all the peoples desire, you are the cornerstone which makes all one. O come and save man whom you made from clay.
Today you could make a crown cake.
December 23rd: O Emmanuel, you are our king and judge, the One whom the peoples await and their Savior. O come and save us, Lord, our God.
Emmanuel means "God is with us." Since Christ is present to us in the Blessed Sacrament, today you could do a Holy Hour with the family.