Yaku
Yaku 「役」 are specific hand patterns or conditions needed in order to score a hand. In a sense, they are synonymous to "poker hands". Yet, unlike poker hands, yaku are worth specific "han values"; and various yaku may be combined together into one hand. basic mahjong knowledge involves learning the yaku, but it is not expected of new players to know them.
Most importantly, every hand must include at least one yaku, in order to count as a winning hand.
Han
Each yaku is assigned han values. Most have static values, regardless of the hand being closed or open. However, some decrease in han value while being open. Furthermore, some also require hands to remain closed in order to count. For hands to maximize the total han value, different yaku may be combined into a single hand.
Open vs closed
Various yaku are affected by the hand's state of being open or closed. After using the different tile calls, a yaku may be affected in terms of han value or even validity. Various yaku, and even yakuman, are restricted to be closed only. Others, they remain valid but their value is decreased by 1-han. As for the rest, it is irrelevant whether the hand is open or closed.
Yaku types
The different yaku focus on different types of patterns and circumstances. They are mostly derived from the tiles within one's hand. A number of yaku also involve the state of one's hand pertaining to the timing of certain tile draws and discards.
Circumstantial
Two yaku specifically are based on the current state of tenpai, as well as particular actions of other players.
- Calling kan with a winning tile.
- Discarding an unsafe tile as the last discard, which happens to be a winning tile.
Discretionary
- This is the only yaku, by which players have the option to declare or not. Otherwise, hands may possibly win without it, if it remains closed with other valid yaku.
Honor based
Honor based tiles depends on the use of honor tile groups. Each of these cases also are mixed with the numbered tiles.
- Honor tiles with one suit.
- Honor tiles with terminals.
- Specific collection of all three dragon types.
- No honors or (terminal) are used.
- Specific collection of any dragon, seat wind, or round wind tiles.
Luck based
Luck based yaku focuses on specific instances regarding tile draws. Sometimes with the exception of ippatsu, other players have no bearing on the outcome of these tile draws.
- Winning before the next tile draw after riichi.
- Winning with the last tile draw.
- Drawing a winning tile after a kan call.
Sequential
These yaku either require sequential tile groups.
- By definition, this yaku uses two-identical sequences.
- A complete string of 1-9 tile naturally use sequences.
- Every tile group must be a sequence.
- By definition, this yaku uses two-identical sequences two times.
- By definition, this yaku uses three identically numbered sequences across the three suits.
Special case
Only one case does not deal with the player's hand but rather on the player's discard.
Terminal based
These yaku revolve around terminals, or complete lack thereof.
- Every tile group with an honor or terminal.
- Only honor and terminal groups.
- Every tile group with a terminal.
- No terminals (or honors) are used.
Triplet
- Can only be formed using triplets.
- Three closed triplets.
- Requires three quads, which are considered as triplets plus one extra.
- Needs three identically numbered triplets across the three suits.
- Triplets of dragon tiles.
- Every tile group is a triplet.
Yakuman
Yakuman is a special class of yaku, by which the pattern itself is awarded the maximum point limit for a single hand pattern.
Combining yaku
Different yaku may be implemented into a single hand. By doing so, the values applied to the different yaku also combine. In short, they stack. This aspect of the game is key towards developing larger scoring hands. With dora, the stacking effect becomes even greater.
External links
- Yaku in Japanese Wikipedia
- Wikipedia listing
- Yaku frequency among Tenhou.net players (Japanese)
- Lists all the yaku occurrences in Tenhou.net by percentages and by room
- Pointing out which yaku to learn first
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