Mentsu

Mentsu 「面子」, known as "tile groups", "melds", or "sets" in English, are used to create a winning hand. They are subdivided into four types: shuntsu (sequence), koutsu (three-of-a-kind), kantsu (four-of-a-kind), and jantou (pair). They are further categorized by their state being "open" or "closed".

Forming these groups is a central part of developing a mahjong hand, because it is required for attaining tenpai and completing hands altogether. Two main factors go towards the formation of these tile groups: suit and number (or type).

The tile groups

Mahjong features four types of tiles in terms of suits: the numbered suits and honors. Every tile group must be of a single suit - therefore, a mix of suits would be invalid.

In addition, honor tiles can only be used by themselves. An honor tile group must be made out of identical copies of one honor tile; you cannot mix different honor tiles together. In other words, honors can be used in pairs/triplets/quads, but not sequences.

Shuntsu

Anjun - Closed	Minjun - Open	Minjun - Open (middle number called)

Shuntsu 「順子」 (sequences) is a tile group consisting of three sequential numbered tiles. Note that 9 does not "wrap around" to 1 - you cannot have sequences of "891" or "912". In addition, you cannot make sequences by using honor tiles.

Self-drawn sequences are called anjun 「暗順」. The open variety are minjun 「明順」. To form a minjun, players are limited to calling tiles from kamicha, or the player from the left. Discarded tiles from the other two players, that are needed to complete this meld cannot be called upon. Furthermore, an added restriction is applied by kuikae, which applies to calls off of previously completed sequences.

Koutsu

Ankou - Closed	Minkou - Open

Koutsu 「刻子」 is a tile group consisting of three of the same type of tiles. In English, koutsu are referred as "triplets". Players may develop minkou 「明刻」 (open triplets) by calling on a discarded tile while already having a pair of said tile.

Kantsu

Main article: Kan

Ankan - Closed	Minkan - Open	Shouminkan - Open (added)

Tile groups involving four-of-a-kind take on a different nature than the other tile groups. Kantsu 「槓子」 must be declared by kan, to be useful. Kan is a special tile call in the game. This call forms a meld from four identical tiles. After the declaration of "kan", then a special set of rules are invoked.

Jantou

Main article: Jantou

This is the pair of the hand, or the jantou 「雀」. The terms mentsu and group do not refer to the pair, but only to the triplets, quads, and sequences.

External links

• 面子

Mentsu in Japanese Wikipedia

• Overview