Naki
Naki 「鳴き」, or "calls", are legal claims on an immediately discarded tile. When an opponent discards a tile you can claim, you can call it to add it to your hand. Upon claiming a discard, the player's hand is then considered open. An open hand is unable to call riichi and is unable to score yaku like menzen tsumo. In addition, some yaku decrease in value after opening. However, opening the hand can allow you to complete it faster.
Properties
For each immediate discard, players may claim a tile if:
- The hand contains 2 out of the three tiles necessary to form a complete meld (see below).
- The claim was made immediately after the discard, before the next player's turn. Otherwise, a discarded tile remains in the discard pile.
- If the discarded tile completes a hand, then any player may call ron, overriding the other tile calls.
Calls are not mandatory. When making a call for a discarded tile (chii, pon, open kan), your hand is considered open. As mentioned above, open hands cannot call riichi, are ineligible for certain yaku, and receive -1 han for certain other yaku.
Any call, except riichi, will immediately invalidate tenhou, chiihou, double riichi, ippatsu, and the option for kyuushu kyuuhai.
Procedure
When making a call, the tiles used for the call are revealed and placed to the side. These tiles are still considered part of the player's hand, but cannot be changed. Therefore, each call reduces the number of tiles you can choose to discard. After making a call, the player discards a tile.
The claimed tile must be arranged sideways to indicate the claimed tile. It must also be arranged on the left, middle, or right to indicate the source of the claim. This notation helps with the enforcement of furiten, as a claimed tile is still a part of the original player's discard pile.
Tile calls
Tile calls can only be formed when it would complete a mentsu or complete a winning hand. These are shown below:
| Chii | チー | Sequences |
| Pon | ポン | Three-of-a-kind |
| Kan | カン | Four-of-a-kind |
| Ron | ロン | Win on discard |
Chii
Chii 「チー」 completes a sequence, to form minjun.
Only the player to the right of the discarded may call chii. In other words, you can only call chii from the left player's discards. Therefore, the tile turned sideways is always indicated on the left. Chii may be particularly subject to the rule of kuikae - when calling a sequence, you cannot discard a tile that would have completed the same sequence. See below for details.
Pon
| Left | Across | Right |
  |
|
|
Pon 「ポン」 turns a pair of identical tiles into a minkou (open triplet).
Unlike chii, pon may be called from any player on the board. Because any player may call, sometimes a player's turn may be skipped.
Kan
Kan 「カン」 are triplets "upgraded" into four-of-a-kinds. Unlike the other calls, kan has some added procedures. In addition, there are three different types of kan:
- Daminkan (open kan) are called like pon, except you need three of the same tile.
- Ankan (closed kan) can be called when four of the same tile are in your hand (without needing to discard a tile). Ankan does not open your hand. You are not allowed to call ankan immediately after calling pon or chii.
- Shouminkan (added kan) can be called when you have previously called pon, then draw the fourth tile yourself. This call turns the called triplet into a kan call.
All forms of kan are still considered triplets, just with one extra tile. Therefore, in order to maintain the hand, one tile is drawn from the deadwall. Also, any form of kan reveals kandora. For more information, see the kan page.
Agari
Agari 「アガリ」 is the generic call for a winning tile. However, this is a general term for the state of winning. It is rare, if ever, do anyone use this term to declare a winning hand.
Ron
Ron 「ロン」 is a specific tile call on a discard, when the discard actually completes the hand. Also, the hand must have a valid yaku. Under furiten, a player may not call ron, otherwise, it is a violation of rules and subject to chombo penalty.
Call precedence
When multiple players can call a tile, the following takes precedence:
- Ron or Agari
- Kan or Pon
- Chii
It is impossible for kan and pon to be called simultaneously. A call for kan requires 3 copies of a tile, the call for pon requires 2 more copies of a tile, but there are only 4 tiles total. It is possible for pon/kan and chii to be called together; the player who calls pon gets the tile. A call for ron/agari will override any other tile call.
Kuikae
Kuikae is a rule which, when making a call, prevents you from immediately discarding a tile that could have completed that call. Under kuikae, calling pon on a 5-pin, then discarding a 5-pin is not allowed. Similarly, after calling chii on a 4-sou with 23-sou, you cannot discard a 1-sou or 4-sou. You are allowed to discard these tiles on any turn afterwards, just not on the turn you made the call. While it is not a fundamental rule, the kuikae restriction is common.
Kuisagari
Kuisagari 「喰い下がり」 is a property of some yaku to lose value when called open. When calling a discard and opening the hand, the player sacrifices 1-han per yaku affected by this rule. This is obviously a negative, though calling allows you to complete the hand faster.
The following yaku are affected directly by kuisagari:
| From 2 han to 1 han | From 3 han to 2 han | From 6 han to 5 han |
|---|---|---|
| Sanshoku | Honitsu | Chinitsu |
| Ittsu | Junchan | |
| Chanta |
Similarly, some yaku can only be scored with a closed hand. Certain yaku, like chiitoitsu and mentsumo, are closed based on their structure or nature. Other yaku, like iipeikou, the requirement of a closed hand is entirely artificial. Unlike instances of kuisagari, you cannot use these yaku to fulfill the yaku requirement of an open hand: these are not considered 0 han yaku. For ryanpeikou in particular, if it were affected by kuisagari, it would score 2 han when opened. But in actuality, you cannot achieve ryanpeikou at all with an open hand.
Finally, some yaku are not affected by kuisagari. Even when open, they retain their original han value. These are yakuhai, toitoi, sanankou, sanshoku doukou, shousangen, sankantsu, as well as any yakuman that can be scored with an open hand.
Atozuke
A side effect to kuisagari involves atozuke. Tile calls may put a hand into position where one of its waiting tiles do not produce valid yaku. With this in mind, tile calls must be made with careful discretion.
Other tile calls
| Kan | カン | Forming a quad |
| Kita | キタ | Picking a North dora |
| Riichi | リーチ | Ready hand declaration |
| Tsumo | ツモ | Win by self-draw |
These tile calls do not apply to discards. Just like the discard calls, these calls are announcements.
Kan
Apart from claiming a discard to form a quad, a quad may also be formed by adding the fourth tile from the hand to the open triplet, or by taking out four identical tiles form the hand.
Kita
In some rules of three-player mahjong, North tiles may be picked and functions as a dora.
Riichi
Riichi 「リーチ」 is a player's declaration for a ready hand. If desired, a player may announce riichi prior to discarding and invoke the rules involving riichi as a yaku. Riichi does not interrupt opponents' tenhou, chiihou, etc.
Tsumo
Tsumo 「ツモ」 is the declaration for winning by self-draw. This may apply to any hand, open or closed. With a closed hand, it also counts as for the yaku, mentsumo. Even when furiten, it is acceptable to win the hand.
Open vs closed
Before making a tile call, players should consider "is it worth opening the hand, or is it better to remain closed?" Naturally, there are advantages to both. For starters, players should know the yaku and their hand values. A closed hand can call riichi and is worth more; an open hand is faster. Players should consider their point standing, hand value, number of tile draws left, and other factors before opening. For more details, see naki strategy.
Yakuman hands, assuming they can be won open, don't reduce in value after a call. Since they are so hard to complete, opening is often necessary to actually win with one.