Yaku

Yaku

Yaku (役, やく) are scoring patterns in Japanese mahjong that you must achieve to declare a winning hand. Without at least one valid yaku, your hand cannot win, even if it has all the necessary melds and pairs. Each yaku contributes han (value points) to your final score, with more difficult patterns worth more han.

Understanding Yaku

The Yaku Requirement

In riichi mahjong, having a complete 14-tile hand is not sufficient to win. You must also have at least one yaku. This fundamental rule shapes all mahjong strategy, players constantly balance between completing their hand quickly and building valuable yaku patterns.

The only exception is riichi itself: by declaring riichi (paying 1,000 points and locking your hand), you automatically create a yaku, even if your hand has no other patterns. This makes riichi a critical safety net for otherwise patternless hands.

Han Value and Scoring

Each yaku is assigned a han value, typically ranging from 1 to 6 han. Simple, common patterns like tanyao (all simples) or yakuhai (value triplet) are worth 1 han. More difficult patterns like honitsu (half flush) are worth 2-3 han. The hardest patterns, called yakuman, are worth maximum points and include hands like kokushi musou or suuankou.

Han combines with fu (minipoints from hand composition) to determine your final payment. More han means exponentially higher scores. For example:

• 1-2 han: Basic hands
• 5 han (or 4 han with high fu): Mangan (2,000 base points)
• 6-7 han: Haneman; 8-10 han: Baiman (doubled mangan)
• 13+ han: Yakuman territory

Open vs. Closed Yaku

Some yaku can only be scored with a closed hand (no called melds), while others work with open hands but score fewer han when open. For instance:

• Menzen-only yaku: Riichi, ippatsu, tsumo, pinfu, these require a completely closed hand
• Open-reduced yaku: Sanshoku (2 han closed, 1 han open), ittsu (2 han closed, 1 han open)
• Open-unchanged yaku: Tanyao (where kuitan is allowed), yakuhai, toitoi

Understanding which yaku work open versus closed is crucial for deciding whether to call melds or keep your hand closed.

Yaku Stacking

Multiple yaku can exist in a single hand, and their han values stack additively. A hand might have pinfu (1 han) + tanyao (1 han) + riichi (1 han) = 3 han total. However, some yaku are mutually exclusive, you cannot have both chanta and tanyao in the same hand, for example, since one requires terminals/honors while the other forbids them.

Example: Yaku in a real hand

You hold a closed hand with sequences of 2-3-4 bamboo, 5-6-7 characters, 3-4-5 dots, 6-7-8 dots, and a pair of 6-bamboo. All tiles are simples (2-8), giving you tanyao (1 han). The hand forms clean sequences with no honors, also qualifying for pinfu (1 han). You declare riichi (1 han) when reaching tenpai. When you win by self-draw, you add menzen tsumo (1 han). Your hand has 4 yaku = 4 han total; at 20 fu (pinfu tsumo) that collects 1,300 from each non-dealer and 2,600 from the dealer.