Riichi Mahjong Primer
This article will attempt to describe how to play riichi mahjong (Japanese Mahjong) online in a simple and concise way. The set-up instructions will be omitted for this guide.
Game overview
Riichi mahjong is a 4-player tile-based board game with a heavy focus on luck. The goal of the game is to collect the most points.
You gain points by assembling winning hands. Winning hands that meet specific criteria score more points.
Each game is sorted into multiple rounds. For every round, only one player can win. A round ends when a player wins, when the tiles run out, or in certain specific conditions.
Turns
At the start of each round, each player is dealt 13 tiles. The East player always starts the first turn, followed by South, West, and North (in that order).
During your turn:
- Draw 1 tile.
- If this tile can complete a winning hand, you may declare a win by self-draw ("Tsumo").
- You may declare a quad ("kan") if conditions allow and if you want.
- You may declare "riichi" if conditions allow and if you want.
- Discard 1 tile.
- Other players may call the discarded tile if they can and want to.
- If the discarded tile is not called, the next player starts their turn.
Tiles
There are 36 types of tiles, and 4 of each type, for a total of 136 tiles. They can be grouped into two major categories:
Number Tiles. Each "suit" of numbered tile has tiles from 1-9. They can be used to form sequences, triplets, and pairs.
- Manzu (Characters) -
- These tiles are labelled in the Chinese characters (equivalent to Japanese kanji) for 1-9. In online play, you'll often have the choice to put arabic 1-9 numbers labels on the top-right corner of the tile.
- Pinzu (Dots, Circles) -
- The number of circles is the number of the tile.
- Souzu (Bamboo, Bams, Sticks) -
- The 1-sou is a bird. The other tiles are green lines, the number of lines is the number of the tile.
Honor Tiles. Each honor tiles has a different character on it. They can be used to form triplets and pairs, but not sequences.
- Dragons
- With dragon tiles, it is not important to know the meaning of the characters are. Thus, they can be referred to as "White", "Green", and "Red" respectively.
- Winds
- These tiles are labelled in the Chinese characters for the winds. In order, they are East, South, West, North. Knowing the wind tiles *is* important. Like the character tiles, the winds can be labelled N S W E in the top right corner if the website allows.
Winning Hands
A winning hand needs to meet two conditions:
- A winning shape. With two exceptions, winning hands are comprised of 4 "sets" + 1 "pair".
- A "yaku". Yaku are conditions that increase your hand's point value. In essence, a hand cannot win with 0 points, therefore a hand cannot win without any yaku.
- (Note: a hand may gain value via "dora" tiles, but if the hand has no value other than dora, it cannot win.)
Both these conditions will be described below.
Winning Shape
First, let's explain what "sets" and "pairs" are.
Sets
Sets, also called "melds", "groups", or "mentsu", are groups of 3-4 tiles of a specific type.
1. Sequences - sequences are three number tiles in sequential order, and of the same suit.
| Closed | Open |
|---|---|
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Sequences may not "wrap around" from 9 to 1, so sequences of 891 or 912 are not allowed. Honor tiles cannot be used in sequences.
2. Triplets - triplets are three copies of the same tile. Any tile can be used in a triplet.
| Closed | Open |
|---|---|
 |
 
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Pairs
Pairs are two copies of the same tile, similar to a triplet.
| Pair |
|---|
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Winning Shape
As mentioned above, with a few exceptions, a winning shape is comprised of 4 sets + 1 pair, for a total of 14 tiles.
Example hand:
4 sets:
- 2 sequences ( ) + )
- 2 triplets ( ) + )
1 pair: ( )
However, you can only hold up to 13 tiles at a time. Therefore, you need to get hand that's 1 tile away from winning ("tenpai"), then either win by drawing a needed tile, or claiming it from another player's discard.
Ready Hand (Tenpai)
A ready hand, or a hand in "tenpai", is a hand that is one tile away from winning. Identifying ready hands is important, since a ready hand is required to win.
Ready hand #1 - 3 complete sets + 1 incomplete set + 1 pair:
3 sets:
- 1 sequence ( ))
- 2 triplets ( ) + )
1 pair: ( )
1 incomplete set ( )
This hand waits to complete the incomplete set of 56-pin. It may win off of:
- , forming a complete sequence, or
- , forming a complete sequence.
Ready hand #2 - 4 complete sets + 1 tile waiting to be paired:
4 sets:
- 2 sequences ( ) + )
- 2 triplets ( ) + )
1 tile waiting to be paired: ( )
It may win off , to complete a pair.
Ready hands may be interpreted in different ways, allowing the hand to win off multiple different types of tiles. For example:
This hand may win off either 
or , to complete a pair.
The section of the hand may be viewed as either ( sequence + tile waiting to be paired) or ( sequence + tile waiting to be paired). Therefore, it can win off either the 4 or the 7.
Yaku
Yaku are specific criteria that gain you points. For example, All Triplets requires all 4 sets to be triplets.To repeat, a hand cannot win with 0 points, therefore a hand must have at least 1 yaku.
A hand can technically gain points with dora tiles. But if a hand has only dora tiles, and no yaku, it still can't win.
The simplest yaku is riichi. So long as you have not called an opponent's discarded tile (you haven't pressed "chii", "pon", and haven't pressed "kan" when it's not your turn), you may declare riichi when you have a ready hand.
More yaku will be covered later in the guide.