Overview
Yaku are somewhat similar to poker hands. They fit certain patterns based on the numbers or types of tiles included, as well as the relative value of the tiles. Unlike poker, however, multiple hand types may be combined to produce hands of greater value.
There are three basic classes of yaku:
- Closed hand only (menzen-nomi, 門前のみ)
- "Eat and decrease" (a literal translation of kuisagari, 喰い下がり), where the han value decreases by one if the hand is open
- Yaku where the han value is the same regardless of whether the hand is closed or open.
Calling for another player's discard to make a meld makes the meld and the hand open. When a winning tile of a closed hand is a discard, the meld including that discard is considered open, while the hand is still regarded as closed. If a hand is closed, the situation is called "menzenchin (門前清)" or "menzen (門前)" in Japanese.
The basic concept of a yaku is that it fits into one of three basic criteria:
- It contains a pattern of some kind
- It has a great deal of consistency, or
- It involves a great deal of luck
Finally, when it comes to points scoring, the total number of han in the hand is counted. When the han value is four or less, fu is also counted. The combination of the han value and fu value corresponds to a points table.
Read more about this topic: Yakuman