rules riichi
Kuitan
喰い断
(くいたん)
Definition
Open tanyao - allowing tanyao to be scored with an open hand. The default rule in ari-ari mahjong but forbidden in nashi-nashi.
Related Terms
Tanyao
断么九
All simples - a 1-han yaku where your entire hand consists only of numbered tiles 2-8. No terminals or honors. Can be open (kuitan) or closed depending on rules.
Ari-ari
アリアリ
A rule set where both kuitan (open tanyao) and atozuke (winning with incomplete yaku) are allowed. The most common modern riichi mahjong rule set.