|English||Terminal in each meld|
3 han (closed)|
2 han (open)
Jun chantaiyao 「純全帯么」 is a terminal based yaku. For this yaku, every tile group and the pair must contain at least one terminal. Additionally, at least one tile group must contain a non-terminal tile, or else chinroutou will be scored instead. Junchantaiyao is similar to chantaiyao, but chantaiyao allows honours in addition to terminals. This yaku is more commonly referred by its shorter name, junchan 「純チャン」.
All portions of the hand must contain a terminal, even the pair. At the very least, all tiles numbered 4, 5, and 6 must be discarded and also the honor tiles. This restriction may slow down the process of developing a junchan hand; and it is only viable and advisable to consider junchan, when the opening hand contains various terminals.
Per the development of the hand, a player is likely forming a junchan hand when the discards show a mix of honor tiles and tiles numbered 4, 5, and 6. Sometimes, the tiles numbered 2 and 3 may be included; as specific terminals may be used for triplets. Furthermore, junchan is often used for open hands, in order to speed up tile development.
Junchan is compatible with a large number of yaku. Because it implies chantaiyao, both cannot be counted with a single hand. Because it requires that the hand have no honours or tiles 2-8, it is incompatible with tanyao, yakuhai, shousangen. A honitsu hand that has junchan would actually be chinitsu. Ittsu cannot be combined as it requires a 456 sequence, which does not include a terminal. Finally, as there are only six different types of terminal tiles, junchan cannot combine with chiitoitsu.
If junchan is combined with toitoi, the hand must contain all terminals, and is thus the chinroutou yakuman. Because junchan is incompatible with chiitoitsu and honroutou must be combined with either toitoi or chiitoitsu, a junchan honroutou is necessarily scored as chinroutou as well.
- Junchantaiyaochuu in Japanese Wikipedia