Mentsu
Mentsu (面子) are the melds used for the game. The melds follow a similar pattern to the regular card game, gin rummy. The melds are subdivided into three types: shuntsu (sequence), koutsu (three-of-a-kind), and kantsu (four-of-a-kind). Forming these melds is a central part of developing a mahjong hand to the point of tenpai and even winning the hand. Two factors go towards the formation of melds: suit and number (or type).
The melds
While the melds are subdivided into three types, they are further subdivided into the state of open or closed.
Shuntsu
Koutsu
Kantsu
Main article: Kan
Kan is a special tile call in the game. This call forms a meld from four identical tiles.