Three different Masses are celebrated on Christmas with three different sets of readings, in addition to the Mass for Christmas Eve Day, which is called the Vigil of Christmas (In Vigilia Nativitatis Domini). A Masses commonly gets its Latin name from the first words of its Introit.
- The Midnight Mass of Christmas (In Nativitate Domini in nocte) is called "Dominus dixit," because the Introit begins "Dominus dixit ad me ..." (The Lord said to me ...).
- The second Mass (In Nativitatis Domini in aurora) is called "Lux fulgebit," because the Introit begins, "Lux fulgébit hódie ... (A light shall shine upon this day ...).
- The third Mass during the day (In die Nativitatis Domini) is called "Puer natus est" (A child is born to us ...).
Image: The Nativity window at Five Wounds Portuguese National Church, which hosts the Immaculate Heart of Mary Oratory.
