Ittsuu vs sanshoku

Hand state, where viability of either yaku is available.

A choice given between two forms of sanshoku (123 or 234) and ittsu.

The two yaku ittsu and sanshoku are not compatible, because the hand does not have enough tile groupings to accommodate both yaku. In turn, this forces players to choose one over the other in the event both are viable during the course of a hand.