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, since 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 they do not count as yaku. Altogether, a hand's points value increases exponentially with every han.
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 (e.g. 2-3-4 of the same suit), 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 ("Eat and decrease", a literal translation of kuisagari, 喰い下がり), or deemed impossible to complete due to the yaku requiring its hand to be closed (menzen-nomi, 門前のみ).
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 melded group is considered open, but the overall hand stays closed (menzenchin 門前清 or menzen 門前).
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 4 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 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 (yakuman), lucky circumstances, and special criteria.
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.
These hands involve terminals and/or honors, or lack thereof (such as tan'yao and yakuhai, due to their simplicity).
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.
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 (役満, or yaku-mangan 役満貫). 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 (ダブル役満).
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 (数え役満) ("counted 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" (Japanese: 役満御三家).
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.
The following are yakuman hands completed on the first go-around.
The following table details yaku and yakuman hands that are usually not recognized as valid but may appear in house rules.