Japanese Mahjong yaku

In Japanese Mahjong, yaku (Japanese: 役) is a condition that determines the value of the player's hand. It is essential to know the yaku for game strategy, although the knowledge is not mandatory. A player must have a minimum of one yaku in their hand in order to legally win a hand. Each yaku has a specific han value. Yaku conditions may be combined to produce hands of greater value. The game also features dora, that allow a hand to add han value, but that cannot count as yaku. Altogether, a hand's points value increases exponentially with every han a hand contains.

Yaku are somewhat similar to poker hands. They fit certain patterns based on the numbers or types of tiles included, as well as the relative value of the tiles. Unlike poker, however, multiple hand types may be combined to produce hands of greater value.

There are three basic classes of yaku:

Calling for another player's discard to make a meld makes the meld and the hand open. When a winning tile of a closed hand is a discard, the meld including that discard is considered open, while the hand is still regarded as closed. If a hand is closed, the situation is called "menzenchin (門前清)" or "menzen (門前)" in Japanese.

The basic concept of a yaku is that it fits into one of three basic criteria:

Finally, when it comes to points scoring, the total number of han in the hand is counted. When the han value is four or less, fu is also counted. The combination of the han value and fu value corresponds to a points table.

The following is a list of all the yaku, their names in English and Japanese, their han values, and any special conditions related to them. They are listed here in groups according to the underlying patterns that define the yaku. Example hands are given, but they are often not the only possible hands with that yaku. All yaku can be divided into seven basic categories, depending on the dominant feature. The features are as follows: patterns based on sequences, patterns based on triplets and/or quads, consistency of the type and numbers of the tiles, lucky circumstances, and special criteria.

To make a declaration, the player calls out “riichi”, discards their tile sideways, and places a 1,000-point stick on the table as a deposit. From this point onward, the player must discard any drawn tile that does not allow them to win. Also, they may not change the content of their hand under any circumstances, with the exception of declaring certain closed quads.

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