Yaku (Japanese mahjong)
In Japanese mahjong, yaku is the primary source of doubling points for a winning player's hand. A one yaku minimum is set for all winning hands, making it essential to know the yaku for basic play. Each yaku is a set of requirements on the shapes of a winning hand that awards an amount of han if the conditions are met. Multiple yaku conditions may be combined to produce hands of greater value. Dora are also crucial to high scoring hands, awarding han instead of fu, but they do not count as yaku. Altogether, a hand's points value increases exponentially with every han up to the mangan and counted yakuman limits.
Overview
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 yaku may be combined to produce hands of greater value. The same applies to limit hands or yakuman, which separate from yaku and dora.All hands start closed. A hand becomes open as soon as the player "calls" a tile discarded by an opponent, in order to complete a group from their own hand. This is called "melding." For example, if a player has in their hand, and an opponent discards a, the first player may call the discard, and thus create a melded triplet. This process can also create melded sequences, and open quads. The calling player must display the completed group by placing the tiles face-up on the table. This makes the hand "open".
Because no open hand can become closed, certain yaku combinations either reduce its value by one if the hand is open, or deemed impossible to complete due to the yaku requiring its hand to be closed.
The only time a player can call an opponent's discard and still have their hand remain closed is when they are calling the winning tile. For scoring purposes, the group with the winning called tile is considered open, but the overall hand stays closed.
The basic concept of a yaku is that it fits into one of three basic criteria:
- It contains a pattern of some kind
- It can consistently be formed during a game, although it does not necessarily need to be common
- It is based on specific game situations, such as discards or actions taken by the players
List of ''yaku''
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 often, many other arrangements are possible for each 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/quads, patterns based on terminals/honors, patterns based on suits, maximum-value hands, lucky circumstances, and special criteria.''Yaku'' based on triplets and/or quads
When the following hands involve triplets, quads are also acceptable. But if they require quads, triplets do not count. Each hand is worth 2 han, regardless of whether the hand is closed or open.''Yaku'' based on terminal or honor tiles
These hands involve terminals and/or honors, or lack thereof.''Yaku'' based on suits
The following two hands are related to a single suit. Both hands lose one han when they are open, and can be stacked with Seven Pairs.''Yakuman'' hands
Certain hands had stringent requirements to complete, with a scoring that automatically award maximum points if completed. This value, along with the hands themselves, are called limit hands, or yakuman. Limit hands are separate from han values, and can stack with other limit hands, but many rulesets do not award more points for this. On the other hand, some rulesets will allow doubling of its points, which is also called daburu yakuman.A limit is always valued at 13 han; any non-limit hands and dora that add up to at least 13 han becomes kazoe-yakuman, so long the hand does not contain any limit hands.
The hands known as Thirteen Orphans, Four Concealed Triplets, and Big Three Dragons are considered relatively easy to complete among limit hands, and are collectively called "the three big families of yakuman".
Some limit hands may have different names in some regions. The names used here come from the World Riichi Championship ruleset, which is also used by the American Riichi Mahjong League.