Advent is a season observed in the Catholic church as a time of expectant waiting and preparation for the celebration of the Nativity of Jesus at Christmas as well as the return of Jesus at the second coming. The term is a version of the Latin word meaning "coming".

The Roman Church has been singing the “O” Antiphons since at least the eighth century. They are the antiphons that accompany the Magnificat canticle of Evening Prayer from December 17-23. 

December 17
O Wisdom of our God Most High,
guiding creation with power and love:
come to teach us the path of knowledge!

December 18
O Leader of the House of Israel, giver of the Law to Moses on Sinai: come to rescue us with your mighty power!

December 19
O Root of Jesse’s stem, sign of God’s love for all his people: come to save us without delay! December 20 O Key of David, opening the gates of God’s eternal Kingdom: come and free the prisoners of darkness!

December 21 
O Radiant Dawn,
splendor of eternal light, sun of justice:
come and shine on those who dwell in darkness and in the
shadow of death.

December 22
O King of all nations and keystone of the Church: come and save man, whom you formed from the dust!

December 23
O Emmanuel, our King and Giver of Law:
come to save us, Lord our God!