The rummy comparison
Rummy games such as gin and canasta use the same core loop as mahjong: draw a card, perhaps pick up a discard, form sets and runs, discard. Beginners who know rummy often find mahjong's turn structure familiar within minutes. Rummikub, a tile-based rummy game developed in the 1930s and 1940s, even uses numbered tiles in coloured suits.
The differences show up quickly, though. Mahjong has honour tiles that can only form triplets, fixed seats with winds, the right to snatch a discard out of turn for a triplet, and scoring that rewards particular combinations rather than simply counting cards left in hand. A mahjong hand also must finish in an exact shape; there is no laying off onto other players' sets.
Chinese card-game ancestors
Historians generally trace mahjong back to Chinese card games played with long, narrow money-suited cards, whose suits represented coins, strings of coins and myriads of coins. Those three suits survive in mahjong as dots, bamboo and characters. Games of drawing and discarding to form sets with these cards were played in eastern China well before mahjong appeared.
Madiao, a trick-taking game with a forty-card deck, and later games such as pengpai and khanhoo-style rummy games, show many of the ideas that mahjong combined: suited ranks, matching sets, and the "peng" claim that survives in mahjong's pung. Mahjong essentially moved these card games onto tiles and added the winds and dragons.
Why tiles instead of cards?
Tiles were already familiar in China through domino games, which used bone pieces marked with pips. Putting the card suits onto tiles made them durable, easy to stand upright in a private rack, and pleasant to handle — and the act of building a square wall from them became one of the game's rituals.
Tiles also changed the feel of the game. They make noise, they can be shuffled face down on the table, and standing them in a row keeps a hand hidden without needing to hold it. The tactile, social quality of tiles is a big part of why mahjong outlived the card games it came from.
What makes mahjong unique
Put together, mahjong's distinctive elements are the four winds and seat order, claiming discards out of turn, the requirement of an exact winning shape, and scoring systems that reward particular patterns. Each regional style adds its own flavour, but those elements are shared.
For a newcomer the practical lesson is simple: borrow your rummy instincts for the draw-and-discard rhythm, but expect the game to reward patience, memory of discards and careful reading of the table far more than rummy usually does.
