Halloween or Hallowe’en, which is less often called Allhalloween, All Hallows’ Eve, or All Saints’ Eve, is a holiday celebrated in many countries on October 31, the night before All Saints’ Day, a Christian holiday. It is the first day of Allhallowtide, the part of the liturgical year when people remember the dead, including saints, martyrs, and all the faithful who have died.

One theory says that many Halloween traditions came from Celtic harvest festivals, especially the Gaelic festival Samhain, which is thought to have pagan roots. Some even say that the early Church may have turned Samhain and the night before into All Saints’ Day. Other scholars think Halloween began as the vigil of All Saints’ Day, a Christian holiday. Halloween has been celebrated in Ireland and Scotland for hundreds of years. In the 19th century, Irish and Scottish immigrants brought many Halloween traditions to North America. By the end of the 20th century and the beginning of the 21st century, Halloween had spread to other countries because of American influence.