Tenpai 「テンパイ」 is also referred to as the "ready hand". It progressed from 1-shanten to effectively 0-shanten. A hand is tenpai or "ready" when only one more tile is needed to complete the hand. The completion may be either done by draw and/or discard, where applicable. Tenpai does not require that the completed hand has a yaku, although both a completed hand and a yaku are necessary to win. Having achieving tenpai is worth some points when a hand ends in ryuukyoku.
The direct opposite of tenpai is noten 「ノーテン」. This word is a contraction of the English not tenpai. A hand in this state absolutely has no chance of winning upon the immediate draw or discard. Instead, it relies on further tile draws and discards to attain the state of tenpai.
Overall, the recognition of a tenpai hand is one of the most important concepts of the game. Without this recognition, then a player lacks the ability to make the best decisions on which tiles to best discard.
Tenpai occurs under any of the four following conditions:
- Three tile groups and a pair (jantou). The fourth tile group needs completion. A majority of wait patterns fall under this condition.
- Four tile groups and a single tile (tanki). Completion occurs when a duplicate of the pair is drawn or discarded.
- Chiitoitsu. Six distinct tile pairs and a single tile (also tanki).
- Kokushi musou.
Every hand in tenpai involves some sort of wait pattern, or machi. Various wait patterns are conveniently named to allow quick recognition of waiting tiles. Likewise, players who recognize these patterns may also be able to select among them.
Jantou are the tile pairs to a mahjong hand. Every hand, open or closed, requires at least one tile paired. The pair must either be in the hand, or the hand must be waiting to complete the pair while in possession of four tile groups. The latter forms the waiting pattern of tanki (pair wait). In addition, certain pairings may generate fu. The tanki pattern generates fu, as well as with certain honor tiles.
Example tenpai hands
For examples 1, 2, and 3, riichi may be called, and/or a player can simply win by self draw. The first two possess yaku without riichi. However, the third example does not, as it stands. It requires riichi, mentsumo, or even the likes of haitei, houtei, rinshan, or chankan to gain yaku. Regardless, the first three are closed tenpai hands.
The last three examples are all open hands. Both 4 and 5 may employ yakuhai. Example 4 definitely has a yaku, via the open call on the green dragon. Example 5 could have a yaku, if the hand is seated west or the game is in the west round. The last example uses hadaka tanki, by which four tile calls were used to achieve tenpai. All that remains closed is a single tile, that needs to be matched with the exact same tile type. However, example 6 does not have yaku as it stands. It'll require haitei, houtei, rinshan, or chankan to gain yaku.
Karaten 「カラテン」, or empty tenpai, is a state where a tenpai hand does not have the ability to win. This is due to unavailability of all instances of winning tiles. The "visible tiles" may either be discarded, used as a dora indicator, or already exist in one's hand. Furthermore, they may be held in other player's hands or even reside within the dead wall. However, the latter case is beyond a player's visibility.
Keishiki tenpai 「形式聴牌」, or shaped tenpai, applies to hands with no yaku. Such hands still remain relevant at ryuukyoku regarding tenpai vs noten payments. The definition of tenpai does not necessarily apply to yaku.
This is a common pitfall for many beginners. Hands are built to tenpai. However, due to lack of or limited knowledge of the yaku, players may find themselves unable to declare a win. Often, the hand simply lacks yaku. Otherwise, furiten may also be a reason. In this state, it is still possible to produce yaku via haitei, houtei, and even possibly rinshan. This is particularly true of open hands. For closed hands, tsumo may count as an additional option.
A dead hand involves a minor penalty, but not subject to chombo. Dead hands often involve minor mistakes, such as a certain number of accidental bumps to the wall or a mistake regarding open calls. A player with a dead hand is never considered tenpai, even if the tiles in the hand show a state of tenpai.
At the end of the hand where all tiles have been drawn other than those in the dead wall, points are rewarded to tenpai hands. Yet, even while in tenpai, players may opt to take the noten penalty, instead of revealing the hand.
Agari 「和がり」 is the general call for a winning hand. Two types of winning calls are more commonly used, depending on the source of the tile:
Proper tenpai hands have a right to make these winning calls. In doing so, players must know which tiles and yaku are needed for a win. Likewise, the recognition of waiting tiles is a necessity to call on the correct tile. Otherwise, improper calls for winning hands result in chombo.
Iishanten, or 1-shanten, is the state of the hand before attaining tenpai. While tenpai is 1-tile away from winning the hand, iishanten is 1-tile away from attaining tenpai.
With regards to tenpai, this may be a critical juncture to the hand as, in order to attain tenpai, the player must discard a particular tile. Ideally, that tile should be a safe tile. Likewise, it may also be a point where the player needs to decide upon riichi or utilize damaten (or hidden tenpai). Regardless, when the hand is at iishanten, a player must be ready to anticipate these kinds of decisions, when tenpai does occur.
- Tenpai in Japanese Wikipedia