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 distinct suits: three numbered suits (manzu, pinzu, souzu), and honors. Each tile group must be composed of a single suit, though a hand can contain tile groups of different suits.

In addition, honor tiles can only make groups with other copies of the same tile; you cannot mix different honor tiles together. As a result, honor tiles cannot be used in sequences.

Shuntsu

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

Shuntsu 「順子」 ("sequences") are a tile group consisting of three consecutive number 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.

Closed 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」 ("triplets") are a tile group consisting of three of the same type of tiles. 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)

Kantsu 「槓子」 ("quads") are special - in order for it to count as a proper tile group, a player must declare "kan". Kan is a special tile call with its own set of procedures: first, the four-of-a-kind must be set aside, then a player must draw a replacement tile.

Kantsu count as triplets for the purposes of yaku.

Jantou

Main article: Jantou

Jantou 「雀」 is the pair of the hand. The terms mentsu and group do not refer to the pair, but a pair is required to complete a mahjong hand.

External links

• 面子

Mentsu in Japanese Wikipedia

• Overview