Machi

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Machi 「待ち」 is the Japanese term for "tenpai wait patterns". Given any mahjong hand at any instance, players are waiting for specific tiles either to develop their hands or complete it. Wait patterns arise during hand development, when mahjong tiles in possession in the hand are in need of other tiles in order to complete mentsu (tile groups) or the entire hand. Wait patterns during tenpai are of particular interest, simply because that is one of the main goals of hand development.

Overview

Many different patterns arise during the course of hand development. Once a hand reaches tenpai, being able to interpret the hand's available winning tiles is a vital skill. If a player does not correctly read their winning tiles, they may miss a valid win, or they may commit a chombo with an illegal win call: either by calling a win on a tile that does not complete the hand, or calling ron while furiten due to a tile that they did not realize would complete the hand.

The most commonly occurring wait patterns have been given names, to make them more easily recognizable. More complex waits can arise involving a large number of potential configurations of the hand. This is especially true of hands with a large number of tiles in the same suit, most notably those aiming for chinitsu. Knowing the basic wait patterns also helps to combine them to interpret complex hands, which may have as many as 8 weights (not counting the special cases of chuuren poutou and kokushi musou, which are easily recognizable).

Hand development

During hand development, it is important to understand the hand's machi for two reasons. The first is that, when trying to bring a hand to tenpai, a player will want to maximize the number of available tiles to bring them closer. Doing this requires interpreting the patterns of potential groups in a similar manner to finding tile waits in a tenpai hand. The second is that furiten is best avoided, and so a player should avoid making discards that would leave them furiten once they reach tenpai. This can be a particular challenge when developing single-suited hands that may have a large number of different waits.

Basic wait patterns

These five are essentially the basic wait patterns. Upon tenpai, they only look to complete either the last tile group or the pair.

Ryanmen

Waiting for:

Penchan

Waiting for:

Shanpon

Waiting for:

Kanchan

Waiting for:

Tanki

Waiting for:

Named combinations

The basic patterns can be combined for more complex patterns; and the wait patterns listed here have taken on names.

Nobetan

Waiting for:

Ryanmenten

Waiting for:

Sanmentan

Waiting for:

Entotsu

Waiting for:

Aryanmen

Waiting for:

Ryantan

Waiting for:

Pentan

Waiting for:

Kantan

Waiting for:

Kantankan

Waiting for:

Tatsumaki

Waiting for:

Happoubijin

Waiting for:

Double Yakuman Patterns

These two unique patterns are linked to specific yakuman. Under all possible tile waits with these patterns, yakuman is ensured; under some scoring rules, winning a hand with these patterns is awarded double yakuman. There are no other wait patterns with more than 8 winning tiles (although it is possible for an 8-sided wait to include four of the same tile in such a way that a hypothetical fifth copy of the same tile would complete the hand).

Chuuren poutou kyuumen machi

Waiting for:

Kokushi musou 13 machi

Waiting for:

Complex patterns

These combinations involve patterns that do not have specific names. Instead, they use combined forms of the other patterns. Furthermore, they mostly consist of consecutive, or closely consecutive, numbered tiles. Recognition of these patterns can produce some significantly powerful waits, which may be immune to suji and have large numbers of waiting tiles.

Related Terminology

Hadaka tanki

'Hadaka tanki refers to when a player has made four tile calls (other than added kans), meaning that they only have one hidden tile left in hand. The hand is necessarily tenpai with a tanki wait. Such a hand is very difficult to defend with, because the player will only have two tiles to choose from.

Jigoku

Jigoku 「地獄」 refers to when there is only one winning tile left to win with. If there is only one wait, this means that the other three copies of the winning tile are all in the player's hand, in a discard pool, in a called group, or visible as dora indicators. If there are multiple waits, this means that all but one of them must be completely used. In English, this is commonly known as the hell wait, a literal translation of the Japanese.

Karaten

Karaten 「カラテン」, or empty tenpai, is the case where there are no tiles left to win with, due to all potential winning tiles already having been used in the player's hand, a discard pool, a called group, or visible as dora indicators. In some rulesets, a hand in this state is considered noten at an exhaustive draw.

Takame and Yasume

'Takame is a potential winning tile which is worth more points than another, called yasume.

External links

Machi in Japanese Wikipedia
Forum list of various patterns
Wait survey quiz in Tenhou.net