FAQ

Another problematic pattern in Mah Jong (besides Chow hand) is one that rewards a player for going out on a "One-chance hand". The pattern is also known as "One-way calling hand", "Filling in the only place", "Only possible tile", or "Single Winner".

1. Classical interpretation

In classical rules this pattern refers to the calling shape of the hand: a hand is said to be "one-chance", if there is only one kind of a tile that completes it into a structurally legal winning hand (it does not matter how many of that tile are still available for play).

a) Calling with a single tile for a pair. Only D2 can complete the hand.

b) Calling with a serial pair for a middle tile of a Chow. Only B5 can complete the hand.

c) Calling with a serial pair for the only possible end tile of a Chow. Only B3 can complete the hand.

d) Either Bamboo 2 or Bamboo 5 can complete the hand. Note that the completing set does not determine whether a hand is one-chance (here a hand can be completed with a pair), but the number of different winning tiles.

e) Either Bamboo 3 or Bamboo 6 can complete the hand. Note that the completing set does not determine whether a hand is one-chance (here a hand can be completed with a Chow B-123 that can be completed only on one end), but the number of different winning tiles.

Note however that classical rules would consider the two examples above as one-chance hands, provided that all four tiles of the other possible winning tile have already been played (meaning that they appear amongst discards and melds).

Accordingly, even a three-chance hand like below hand could be considered one-chance in classical rules:

f) A hand that can be completed with Bamboo 1, 4 or 7. Even this hand would be considered one-chance, assuming that all four tiles of Bamboo 1 and 7 appear amongst discards and melds. Note that the tiles in a player's own hand are not considered as played, so if three Bamboo 4's appear on the table, Bamboo 4 would not be considered exhausted, even if there actually are no more of them available as one appears in a player's own hand.

Note that the number of possible different winning tiles is determined strictly by the calling shape and it is not effected by possible restrictions on the winning hand (e.g., if the rules apply a minimum point requirement, or restrict the number of Chows, the number of possible winning tiles is not reduced because of these restrictions). The only possible reason for a certain winning tile to be considered as "dead" is that it has been already played four times.

Note: Classical rules give any hand that goes out on a pair an extra bonus of 2 points, but this is handled separately from "one-chance". Thus a hand described in example (a) would receive bonus for being both one-chance and going out on a pair.

2. Other interpretations

The above described classical concept is rarely used in modern versions Mah Jong. If the pattern is used at all, it is most often interpreted in a way that it is customarily applied in Japanese rules and modern Chinese rules: any hand that can be completed with a pair or a one-chance Chow is considered "one-chance".

g) Either Bamboo 2 or Bamboo 5 can complete the hand. If a hand goes out on Bamboo 2, a player is free to arrange the hand so that the completing set is considered to be the pair (and not the Chow of Bamboo 2-3-4).

h) Either Bamboo 3 or Bamboo 6 can complete the hand. If a hand goes out on Bamboo 3, a player is free to arrange the hand so that the completing set is considered to be either the one-chance Chow of Bamboo 1-2-3 or the pair of Bamboo 3 (and not the Chow of Bamboo 3-4-5).

It is possible that this interpretation is originally a result of using examples of one-chance hands out of their proper context: e.g., if the first three examples (a to c) are used without explaining the requirement for one kind of a possible winning tile (which excludes hands that can go out on more than one possible different winning tile), the obvious result is that any hand that goes out on a pair or a one-chance Chow is considered "one-chance". Anyway, this interpretation is so common in modern Mah Jong that there is no point in trying to "correct" it.

On the other hand, some rules mix the above two interpretations and might e.g. acknowledge as "one-chance" any hand that goes out on a one-chance Chow (including multiple-chance hands like in example h), but on the other hand might consider the following kinds of hands as not qualifying as "one-chance":

i) A multiple-chance hand that can go out on either Bamboo 2 or a Bamboo 5. A hand is not considered one-chance even if it goes out with a pair.

These kinds of interpretations are clearly results of a poorly understood original rule and should be avoided as confusing: there is no point in accepting multiple-chance hands that go out on a one-chance Chow (as in example h), and denying hands given in example i) above, since it is statistically often more difficult to complete the latter (though if the probability argument is used, it could well be argued that it is not reasonable to reward any multiple-chance hand going out on a pair or a Chow, as completing a hand that is calling with e.g. B22 44 and goes out on a triplet would be statistically even more difficult).

Finally, some rules interpret the pattern simply as going out on any tile three pieces of which are already visible on the table (amongst discards and melds) – some players count the tiles in a player's own hand also as "visible" (or played) tiles.

j) A multiple-chance hand that can go out on either Bamboo 2 or a Bamboo 5. If the hand goes out on Bamboo 5, it is considered one-chance simply because it goes out on the 4th instance of Bamboo 5 (the other three appear as melds or discards).

Though this pattern is sometimes acknowledged (amongst dozens of other) in modern pattern-based Asian Mah Jong, it is likely that if this pattern appears in Western Mah Jong, it is based on poorly understood or inadequately translated original rule.

3. Examples of variations of "one-chance" patterns

Most of the different variations are supported in Four Winds 2 by the following four patterns: One-chance hand, Out on a pair, Out on a one-chance Chow and Out on 4th of its kind. In addition, the following related special cases are also supported: Last-chance hand, Out on last of a one-chance Chow and Out on last of a multi-chance Chow.

The table below describes how "one-chance" patterns is interpreted in different rules:

Rules	Pattern (in Four Winds)	Options (No = Not applied)	Description of interpretation
Chinese Classical	One-chance hand	Allow dead multiple-chance hand (Yes); Consider player's own hand tiles as "played" (No)	Classical interpretation, allowing dead multiple-chance hands. Note that classical rules give additional 2 points for both Out on a pair and Out on a major pair.
	Out on a pair	–
	Out on a major pair	–
Dutch League Rules	One-chance hand	Allow dead multiple-chance hand (No); Consider player's own hand tiles as "played" (No)	Classical interpretation, but does not allow dead multiple-chance hands. Note that rules give additional 2 points for Out on a pair.
Dutch League Rules	Out on a pair	–
German	One-chance hand	Allow dead multiple-chance hand (No); Consider player's own hand tiles as "played" (No)	Classical interpretation, but does not allow dead multiple-chance hands.
Italian	Last-chance hand	Consider player's own hand tiles as "played" (Yes); Allow dead multiple-chance hand (Yes)	Going out on the 4th tile of an only possible kind of winning tile that can complete a hand. E.g., calling with B-222 34 and going out on B2 is accepted, if four B5's have been played, as B2 is the 4th instance of the only possible winning tile.
Chinese New Style / Japanese Classical / Japanese Modern / Japanese Transitional / Taiwanese 16-tile Mah Jong / European Classical / Australian	Out on a pair	–	Going out on any pair or any one-chance Chow is considered "one-chance". A player is free to arrange his hand in a way that produces the best scores.
	Out on a one-chance Chow	–
Chinese Official	One-chance hand	–	Classical interpretation, but does not allow dead multiple-chance hands. In addition, the rules give a bonus for going out on 4th instance of a tile (the other three must appear amongst melds and discards).
Chinese Official	Out on 4th of its kind	Consider player's own hand tiles as "played" (No)
Wilmington Advanced 12-Tile Rules	Out on a pair	–	Going out on any pair or any one-chance Chow is considered "one-chance". A player is free to arrange his hand in a way that produces the best scores. Additional points are rewarded for going out on the last tile of a one-chance Chow, or last tile of a multiple-chance Chow. E.g., calling with B22 46 and going out with B5 is considered Out on last of a one-chance Chow, if three Bamboo 5's appear on the table amongst the melds and discards, and calling with B22 56 and going out with B4 is considered Out on last of a multi-chance Chow, if three Bamboo 4's and four Bamboo 7's appear on the table amongst the melds and discards. In addition, a bonus is given for going out on number 5 in a Chow 4-5-6 (note that number 5 is actually required, this does not apply to any middle tile in a one-chance Chow).
	Out on a one-chance Chow	–
	Out on last of a one-chance Chow	–
	Out on last of a multi-chance Chow	Allow 1 of both end tiles (No)
	Out on 5 of a Chow 4-5-6	Require self-drawn (No)
American Classical	Out on a pair	–	Going out on any pair is rewarded with a bonus of 2 points.
Alan's Zung Jung / American Modern / British Official / French / Hong Kong/ Internet Mahjong Server/ Korean Style / Mahjong Masters Million / WMPA	–	–	These rules do not acknowledge any kind of a "one-chance" pattern.

What is a one-chance hand?