What do Christians call the birth of Jesus Christ?

The Nativity or birth of Jesus Christ is found in the biblical gospels of Matthew and Luke. The two accounts agree that Jesus was born in Bethlehem, modern-day Palestine, in Roman-controlled Judea, that his mother, Mary, was engaged to a man named Joseph, who was descended from King David and was not his biological father, and that his birth was caused by divine intervention. The Nativity is the basis for the Christian holiday of Christmas and plays a major role in the Christian liturgical year. Many Christians traditionally display small manger scenes depicting the Nativity within or outside of their homes, or attend Nativity plays or Christmas pageants focusing on the Nativity cycle in the Bible.

Source: Wikipedia