The word Xmas, like fruitcake, is one of those holiday traditions that everyone knows of but no one quite understands. Is it proper English to shorten Christmas to Xmas? Is it offensive? No one seems quite sure. So my Xmas gift to you is a quick clarification.

Contrary to popular belief, Xmas is neither an error nor an attempt to take the Christ out of Christmas. The X comes from the Greek letter chi, which is the beginning of Khristos, the Greek word for Christ. In Greek, the word looks like this:

The Oxford English Dictionary dates the use of X to mean Christ back to 1021 AD and the use of Xmas back to 1551 AD, so if you choose to write the word, you have a long history of legitimate usage backing you up.

However, you should be warned that style guides frown on the use of Xmas. The AP Stylebook admonishes, “Never abbreviate Christmas to Xmas or any other form.” The New York Times Manual of Style and Usage agrees about Xmas, commanding, “Do not use; spell out Christmas.”

And keep in mind that if you use it, you also risk offending Christians who aren’t aware of the word’s origin.

So when can you use Xmas? I thought of four scenarios:

• If you’re making your own holiday cards, and you want the letters to fit on the page easily
• If you’re writing a tweet, and the extra five characters in Christmas would put you over the 140-character limit
• If you’re sending a text message on a flip phone, and typing Christmas will take significantly longer than typing Xmas
• If you’re a natural contrarian, and you enjoy explaining to people that using Xmas is not actually wrong

Don’t do that last one if you work for a newspaper. Can you think of any other occasions to use Xmas? Leave them in the comments.

And have a very merry Xmas.