Yaku variations
Different yaku may be subject to rule variations. The variations may include altering the different strengths of the yaku, in relation to point values. A number of yaku are simply not considered standard.
Chiitoitsu
Under most practices, chiitoitsu requires 7 unique pairs.
Daburu riichi
Score riichi as 2 han yaku instead of 1 han if called within the first uninterrupted go-around of a hand.
- Ari – Score daburu riichi as 2 han instead of 1 han.
- Nashi – Always score 1 han per riichi declaration.
Haitei and houtei
Score the 1-han yaku haitei raoyue for winning with the last tile from the live wall, or score the 1-han yaku houtei raoyui for winning on a discard while the live wall is empty.
- Ari – Both yaku are allowed.
- Nashi – Neither yaku is allowed.
Haitei and rinshan
When a kantsu is declared with exactly one tile left in the live wall, that tile, called the haiteihai, is appended to the dead wall and never drawn. This rule makes the replacement tile the haiteihai, so winning with that tile scores both rinshan kaihou (winning after kan) and haitei raoyue (winning with the last tile).
- Ari – Allow this combination. I consider this a bug in the 2012 EMA RCR.
- Nashi – Do not allow this combination. This is Japanese default.
Ippatsu
Score an additional han for winning a riichi declaration within the next go-around.
- Ari – Score ippatsu as an extra 1-han yaku.
- Nashi – Don't score ippatsu.
Kazoe yakuman
Score a hand with 13 han or more as a yakuman.
- Ari – Score as a yakuman with 8,000 basic points.
- Nashi – Score as a sanbaiman with 6,000 basic points.
Kokushi and chankan
Sometimes, it is allowable for a tenpai kokushi musou to declare ron on an ankan and thereby invoking the ability for chankan.
- Ari – Allowed
- Nashi – Disallowed
Multiple yakuman
Score each of the listed patterns as a double yakuman.
- Nashi – All yakuman count as single yakuman. See combined yakuman below for another possibility to score a multiple yakuman.
- D – Daisuushii may be scored as double on its own, or else relegated to a single.
- S – Suuankou tanki may be scored as double on its own, or else relegated to a single.
- K – Kokushi musou shiisanmen machi : Thirteen orphans winning from the thirteen-sided wait on the pair.
- 9 – Junsei chuuren poutou : Nine heavenly gates winning from the nine-sided wait 1112345678999.
Different yakuman patterns may be combined. However, scoring is handled differently as well. Score more than one yakuman if multiple yakuman are achieved by the same hand.
- Ari – Add one yakuman per single yakuman, add two yakuman per double yakuman if allowed, and score the sum.
- Nashi – Score only one yakuman per hand, or two yakuman if double yakuman are allowed.
Optional yaku
The main list of yaku does not include various other possible tile combinations, as they are not accepted as "standard yaku". With this, house rules may include additional yaku to the list, if desired. The following are particularly common examples; the optional yaku page contains more detailed rules and many more yaku.
Daisharin
Daisharin is an optional yaku. This involves a closed hand with pairs of each of the simples of the suit, pinzu. Sometimes it is regarded as a yakuman. Otherwise, the hand is counted normally with its yaku counterparts. The hand is at least 11 han with a combined chinitsu, ryanpeikou, tanyao, and pinfu.
Agari:
- Ari – Score this hand as a yakuman.
- Nashi – Score this hand normally.
For souzu and manzu, the hands are labeled as daichikurin and daisuurin, respectively.
Open riichi
Allow players to declare open riichi instead of a normal riichi. Open riichi is worth 2 han instead of the normal 1 han. The declarer must reveal his hand at the same time as he pays the bet of 1,000 points.
- Ari – Allow open riichi along with normal riichi.
- Wait shape – The declarer only needs to reveal 1, 4, 7, or 10 tiles if these completely describe the wait shape of the hand. The pair or pair wait must always be revealed.
- Nashi – Don't allow open riichi.
Sometimes, directly playing into an open riichi (ron) is penalized by yakuman value.
Paarenchan
Score the eighth consecutive win of the same dealer as a yakuman.
- Ari - Yakuman scored.
- Nashi - Eighth hand scored normally.
Renhou
This is a yaku for winning on a discard before the winner's first turn in an uninterrupted go-around.
- YMan – Yakuman: Score this as a yakuman. No other yaku is necessary.
- M – Mangan: Score this as a mangan. No other yaku is necessary. If a regular count of the hand would give haneman or better, the normal scoring is used.
- Yaku – Renhou functions as a regular yaku, with an assigned han value. As a regular yaku, it is capable of combining with other yaku.
- Nashi – Renhou is not a yaku. The hand is scored normally, there must be at least one other yaku present for a valid win.
Pao
Pao applies to an alternative point exchange, in the event of making foolish discards, which gives players particular advantages.
Daisangen and daisuushii
Impose a liability payment on the player who has dealt the third pon/kanned dragon tile, or the fourth pon/kanned wind tile, if the caller wins with daisangen (big three dragons) or daisuushii (big four winds) later.
- Ari – Liable player pays full on tsumo, half on ron.
- Nashi – No liability for daisangen or daisuushii.
Suukantsu
Impose a liability payment on the player who has dealt the fourth kanned tile, if the caller wins with suukantsu (four kantsu) later.
- Ari – Liable player pays full on tsumo, half on ron.
- Nashi – No liability for suukantsu.
Daiminkan rinshan
Require that a player pay for a hand, as for a ron, when his or her discard is called for daiminkan and the caller wins a tsumo for rinshan kaihou on the replacement tile.
- Ari – Player dealing into daiminkan pays for the whole hand.
- Nashi – All players pay for the hand, as normal for a tsumo.
Nagashi mangan
Score a mangan upon exhaustive draw for having discarding only yaochuuhai during the entire hand, with none of the yaochuuhai having been called by other players, and without having called any tiles oneself. If this is allowed, there are additional rules decisions necessary: Does it count as a win, or merely as replacement of the noten penalty? Are concealed kantsu allowed?
- Ari – Score nagashi mangan, but I don't know the details.
- Ari B – Score nagashi mangan as a replacement of the noten penalty, not as a fully-fledged win. I don't know what happens if you declare ankan, that will likely prevent nagashi mangan.
- Ari KW – Score nagashi mangan as a win (W), voiding noten riichi chombos and collecting riichi bets and honba payments. It is legal to declare a concealed kantsu (K) and still score nagashi mangan.
- Nashi – Don't allow nagashi mangan.
Rinshan fu
Award a hand winning with the rinshanpai (kan replacement tile) the usual 2 fu for winning with a self-drawn tile.
- 2 fu – Award the hand 2 fu for tsumo.
- Nashi – Don't count any fu for tsumo on the rinshanpai.
Ryuuiisou
A limit may be imposed on ryuuiisou to include or exclude hatsu.
- Incl – Include hatsu
- Req – Require hatsu
- Excl – Exclude hatsu
Tenhou and chiihou
Score a self-drawn win within a hand's first uninterrupted go-around as a yakuman.
- Aari – Score tenhou and chihou as yakuman.
- Nashi – Score these wins as normal hands.