Shanten

Shanten 「向聴」 is the number of tiles needed for reaching tenpai. It can also be viewed as the minimum number of tile draws or tile calls required to attain tenpai.

Shanten counts

The lower the shanten count, the closer the hand is to tenpai. Naturally, that is advantageous as far as tile efficiency is concerned. After all, the sooner the hand gets to tenpai, then the sooner can the hand win. For every shanten count, the hand needs any needed tile just to reduce that count.

Iishanten

Example: 1-shanten

Needs: Any to tenpai.

Ryanshanten

Example: 2-shanten

Needs: Any to 1-shanten.

Sanshanten

Example: 3-shanten

Needs: Any to 2-shanten.

Open vs closed

Main article: Naki

Often, the decision to open the hand rests on the tiles needed and the yaku most conveniently acquired. In addition, the shanten count may play a factor too, especially at 1-shanten where a discarded tile could put the hand into tenpai.