Furiten
Furiten 「振聴」 is a restriction applied to tenpai hands. While in furiten, the player loses the ability to declare a win on any player's discard (ron). The most common form of furiten is with discards: if any tile the hand could have won off is in a player's discard pile, it is furiten. This includes any tiles called by opponents. Other cases involving riichi and temporary furiten are also applicable. Regardless, the hand can still win by self-draw (tsumo) given valid yaku.
This rule is often used for defense purposes to determine safe tiles. Tiles with the furiten rule can be inferred via suji, though this may not be guaranteed.
Rule statement
A hand in tenpai is in furiten in any of the following scenarios:
- At least one winning tile is in one's own discard pile. This applies even if the hand could not actually win off that tile (due to lacking yaku).
- The hand is declared riichi and the (first) winning tile is not claimed. This is known as permanent furiten.
- The hand is not declared riichi, another player discards a tile, and the winning tile is not claimed, even if the hand could not actually win. Then the hand is in temporary furiten and cannot ron until the player has discarded.
While in furiten, the hand is unable to call ron upon a discard. However, it is still winnable via self-draw, assuming the hand has valid yaku. Note: when any winning tile triggers furiten, the entire hand is furiten.
Discard furiten
     
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The most common case of furiten involves a player's own discard. If a winning tile is in a player's discard, then the hand is in furiten.
All of a player's discards can be checked at any time during play, by looking at their discard pools and the rotated tiles in other players' tile calls. This leads to the most basic strategy to avoid dealing into a player's hand: tiles they have already discarded are guaranteed to be safe against a ron call from that player.
During hand development, it is important to bear furiten in mind. Most of the time, if a hand gets to tenpai and is furiten at that point, it indicates that the hand was inefficiently developed. This is not always the case, as sometimes a player makes a tactically correct decision and finds themselves in furiten anyway.
The most common reason for furiten, however, is when a player is already tenpai with an open hand, and does not have a guaranteed yaku. While they may have a winning tile that provides them with a yaku, if they draw another tile which completes the hand without a yaku, then they will be forced into furiten on the next discard. This most commonly occurs when the hand has:
- A shanpon wait, with one tile completing a yakuhai triplet, and the other having no yaku.
- A ryanmen wait on 14 or 69 on a hand that would otherwise complete tanyao.
These type of cases are known as atozuke.
Finally, a player considering a double riichi should carefully inspect their hand before discarding; if they had a complete hand to begin with, then being in furiten will add insult to the injury of having [passed] on a tenhou or chiihou tsumo.
Example tenpai hand
Waiting for: 
This hand waits on three different tiles. If the player has a 2-pin in their discard pile, then the hand is in furiten and may not win by ron on any tile. Even if a 5-pin or 8-pin gets discarded by an opponent, ron may not be called.
Temporary furiten
Any player in tenpai has the option to ignore a winning tile. By declining a call for ron, the player then becomes temporarily furiten until their next discard. This is called temporary furiten, as it expires shortly after it occurs. This applies to a discarded tile, as well as tiles used to create a shouminkan. Ankan are exempt: the only hand that can ron of an ankan is a single-sided kokushi musou, and if ron happens to be skipped, the hand becomes impossible.
The primary purpose of the rule is to prevent a player from targeting a later player in the turn order. Once a player sees a tile discarded, they know that they can follow with the same tile and it will be safe for that turn.
While this is often a mistake to enter temporary furiten, done by a player who does not know their waits correctly or is not paying attention, it may be done deliberately in order to achieve a higher scoring hand or to target a specific player. This becomes much more common in orasu, where a player may gain little benefit from winning a hand that does not let them pass another player. Temporary furiten can also be entered by a player who does not have a guaranteed yaku, as described above. This is much less devastating than drawing the yasume tile, however, because it is only temporary.
Uncommonly, some rulesets vary the rules by allowing a tile call made by another player to cancel temporary furiten. This variation is considered by many to be a poor one.
Permanent furiten during riichi
When a player has declared riichi, the state of temporary furiten does not expire. Per the rule of riichi, a player cannot change wait. Therefore, the hand can no longer be adjusted to escape furiten. The only one opportunity to call ron comes from the first instance of a winning discarded tile. If the call to win is declined, then the only option to win the hand comes via tsumo. This rule is a critical part of defense against riichi, as it means that any tiles discarded since the declaration is safe to the riichi called player.
A player in riichi never has to worry about yasume putting them in furiten unless they are playing with ryanhan shibari. When ryanhan shibari, a riichi without a guaranteed second yaku may be quite dangerous due to furiten.
Strategy
Defense
The furiten rule may be applied for defensive play, which focuses on discarding safe tiles. By discarding tiles that are also visible in an opponent's discard pile, a player can avoid a ron call by that opponent. Likewise, usage of suji and kabe may also help players deduce safe tiles, based on opponent discard. This is applied when a player does not have any matching tiles in the hand with opponent discard; or a player may rather keep certain tiles, for the sake of developing the hand without tearing it apart.
Working with furiten
Sometimes, it may be necessary to deliberately place the hand in furiten. Often, this is the result of developing the hand and defending simultaneously. To escape the bind applied by furiten, then the hand's tile wait(s) must simply change by adjusting and changing the tiles in the hand with subsequent tile draws. Of course, a player may place greater expectation on tsumo to win rather than ron.
On rare occasions, a player may hold a tenpai hand with damaten. The hand may invoke riichi, but the player had chosen not to for some reason. Eventually, a winning tile may arrive; and instead of declaring a win, the player opts to call riichi. That instantly puts the hand in furiten opting to win by tsumo later.
Furiten tsumo
Hands in furiten can still win, as furiten imposes a limit of tsumo only. For open hands, the hand requires a valid yaku. For closed hands, mentsumo will be acceptable or added.
External links
- Furiten in Japanese Wikipedia