In American English, and this might come as a surprise (or perhaps not) to my British readers, the preferred spelling is pajamas. Now I know what you're thinking: there go the Americans, messing around with the English language again. Well, as ever, the answer is not quite that simple.
Firstly we have to go back to the origins of the word. As an item of clothing, pyjamas were first worn by Muslims in India and were referred to not (I hope you're sitting down for this one) as P.J.s, but as pai jamahs (from around 1800). Later, this evolved into the Hindi word pajama, at or around the time the garments became popular across Europe.
Notice anything interesting about the two early versions of the word? Pai jamahs probably reads as PY-JAHM-AZ to Western readers—perhaps accounting for the preferred present day spelling that exists outside of North America. However, you will notice that within the spelling of both pai jamahs and pajama the initial vowel sound is represented not by the letter y, but the letter a—lending credence to the present day American spelling.
Indeed, this very spelling is first attested from 1845. It was during the first half of the 19th century that many American spelling variants (color, meter, theater etc.) fell into standardised usage, following the publication of Noah Webster's dictionary (1828). Moreover, a new edition of that very resource book was published in 1845—the first to feature the Merriam imprint after the Merriam-Webster merger.
It is quite possible, therefore, that the word pyjamas—containing a needlessly complex representation of the initial vowel sound—was altered by American lexicographers (Webster had died in 1843) at this time. Whichever way you slice it, though, the American spelling is more in line with early versions of the word and, if anything, you could say it was the British who "messed with the English language."
That said—as with all British/American language differences—I would never presume to deem either usage incorrect. However, when it comes to actually wearing pyjamas, I'm very firmly in the "no" camp. But you probably didn't care to know that.
How do you spell pyjamas/pajamas? Also, do you even wear them? Let us know in the comments below.
This article was written by Laurence Brown. Laurence is a British expat living in Indianapolis, Indiana. He is a contributor for BBC America and has written for Anglotopia. He is Editor-in-chief of Lost in the Pond and loves nothing more than to share these articles with anglophiles, expats, and other interested parties on social media. Follow Lost in the Pond on Facebook, Twitter and Google+.