Quick answer
Mah Jongg and mahjong are both correct. Mah Jongg, with a double g, is the traditional American spelling, used by the National Mah Jongg League on its card and dating from Joseph Babcock's 1920s trademark Mah-Jongg. Mahjong, one word, is the standard modern English spelling for the game in all its forms.
You see 'Mah Jongg' on the League card, 'mahjong' in the newspaper, 'mah-jongg' in a 1920s ad, and 'mahjongg' on a solitaire app, and wonder if you've been spelling it wrong all along. You haven't. Here's the two-minute history that explains every variant.
Where the spellings come from
The game is Chinese, 麻將 (májiàng), and when Joseph Babcock imported it to America in the early 1920s he coined and trademarked the spelling 'Mah-Jongg', double g, hyphen and all, as a brand name for his sets. The craze outlived the trademark, but the double-g spelling stuck in American tradition.
When the National Mah Jongg League formed in 1937 to standardize the American game, it kept the traditional double-g spelling, 'Mah Jongg.' That is why the yearly card and League materials still write it that way.
Meanwhile, the rest of the English-speaking world settled on the simpler one-word 'mahjong', it is the spelling used in dictionaries, in news coverage and in app stores, and the one search engines treat as the default.
So which is correct?
Both. 'Mah Jongg' (double g) signals the American game and the League's tradition, while 'mahjong' is the standard modern English spelling for the game in all its forms. They are the same word wearing different decades' clothes.
Our house style is to write 'American Mahjong' for clarity and searchability, and we honour 'Mah Jongg' as the traditional American spelling, the one printed on the League's card.
Telling the games apart from the words on the page
The practical value of knowing the spellings is that they travel with different vocabulary, and the vocabulary tells you which game a page, a video or a product is actually about before you spend an evening on the wrong rules.
If a page talks about the card, the Charleston, jokers or racks, it is describing the American game. Each of the four is an American feature. The card is the yearly list of legal hands, the Charleston is the passing ritual before play, the jokers are the eight wild tiles, and the racks hold and display your tiles. A page that never mentions them, and instead discusses bonus tiles, seasons scored separately, or hands built from suits and honours with no printed list, is describing one of the other styles.
This matters because the two are different games sharing a tile set. Learning the wrong one first is how a beginner ends up at an American table holding rules that do not apply.
What to type when you are buying or looking for a group
When buying a set, search American mah jongg set rather than mahjong set. An American set has 152 tiles including eight jokers and comes with four racks. A set sold as 144 tiles is built for the Chinese game and has no jokers, so it will not work here without adding them.
When looking for people, search American mah jongg followed by your town or county. That search finds clubs, libraries and community centres, because those groups describe themselves the way the League does. The one-word spelling pulls in the solitaire tile-matching app, which is not this game at all.
When looking for rules, add American to whatever you were going to type. It is the word that separates the game you are learning from every other thing called mahjong.
Why it matters when you search
Search engines treat the spellings as near-synonyms, so you'll find your way regardless. But know the pattern. 'Mahjong' alone often surfaces the solitaire tile-matching computer game (a completely different thing). Searching American mahjong instead gets you the four-player game with the card, the Charleston, and the jokers. That's the game this school teaches.
Put it into practice
New to the game? Start the course at Lesson 1, Meet the Tiles. The first three lessons are free and need no account.
Already play? Have the coach read a real dealt hand for you, free. It names the direction the hand goes for, what to keep, what to pass, and the reasoning behind each call.
However you spell it, the skill that decides a game is reading your own tiles. Mei, our AI coach, reads a hand tile by tile, says which direction it goes for, and what to keep and what to pass, free.