Xmas is a common abbreviation of the word Christmas. It is sometimes pronounced, but Xmas, and variants such as Xtemass, originated as handwriting abbreviations for the typical pronunciation. The 'X' comes from the Greek letter Chi, which is the first letter of the Greek word Christós, which became Christ in English. The suffix -mas is from the Latin-derived Old English word for Mass.

Christmas is an annual festival commemorating the birth of Jesus Christ, observed primarily on December 25 as a religious and cultural celebration among billions of people around the world. A feast central to the liturgical year in Christianity, it follows the season of Advent or the Nativity Fast, and initiates the season of Christmastide, which historically in the West lasts twelve days and culminates on Twelfth Night. Christmas Day is a public holiday in many countries, is celebrated religiously by a majority of Christians, as well as culturally by many non-Christians, and forms an integral part of the holiday season surrounding it.