Yaku

Also called: 役, scoring pattern

Japanese-only term for a named scoring pattern. Every winning Riichi hand needs at least one yaku.

Yaku is the Japanese term for a scoring pattern. Riichi mahjong specifically requires at least one yaku to declare victory — without a yaku, you can have a structurally winning hand but cannot call ron or tsumo. Each yaku is worth 1-13 han. Examples: Riichi (1 han), Pinfu (1 han), Toitoi (2 han), Kokushi Musou (13 han / yakuman).

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Related terms

Han
Riichi scoring unit — counts each yaku in your hand.
Yakuman
Riichi's limit hands — instant 13-han equivalent, payout capped at the table limit.
Fu
Riichi's secondary scoring axis — small points for hand structure and wait shape.