Japanese mahjong yaku

In Japanese mahjong, yaku (Japanese: 役) is a condition that determines the value of the player's hand. It is essential to know the yaku for game strategy, since a player must have a minimum of one yaku in their hand in order to legally win a hand. Each yaku has a specific han value. Yaku conditions may be combined to produce hands of greater value. The game also features dora, that allow a hand to add han value, but they do not count as yaku. Altogether, a hand's points value increases exponentially with every han.