Souzu

Souzu

Souzu (索子, そうず) is the bamboo suit in riichi mahjong, where each tile shows a number of bamboo sticks equal to its value, except for the 1-souzu, which shows a bird instead of a single bamboo stick. There are 36 souzu tiles in a standard riichi set (4 copies of each value 1-9). The bird on the 1-souzu is the single most distinctive design element in any mahjong set.

Understanding Souzu

Visual Identification

Souzu tiles 2 through 9 show their value as a count of vertical bamboo sticks:

• 2-sou: two sticks vertically
• 3-sou: three sticks
• 4-sou: four sticks (often in a 2-over-2 arrangement)
• 5-sou: five sticks (typically 1 center + 2 above + 2 below)
• 6-sou: six sticks in two rows of three
• 7-sou: seven sticks (one above, three over three is common)
• 8-sou: eight sticks in two rows of four
• 9-sou: nine sticks in a 3-by-3 grid

The 1-souzu is the exception. Instead of a single bamboo stick, it shows a stylized bird, often a peacock, sparrow, eagle, or phoenix depending on the manufacturer. The bird is always clearly labeled as the 1 of bamboo even though it doesn’t visually match the rest of the suit.

Why the Bird?

The bird design replaced what would have been a single bamboo stick because a single vertical line was too easy to confuse with similar designs on coin tiles or even on the 萬 character at the bottom of manzu tiles. Manufacturers added a recognizable bird image to make the 1-souzu unambiguous.

The choice of a bird connects to mahjong’s older Chinese name: 麻雀 (máquè in Mandarin; maajan in Japanese), which literally translates as “sparrow.” So “the bird tile” is a small visual nod to the game’s name itself. Most modern riichi sets use a peacock or stylized phoenix for the 1-sou, but you’ll occasionally see eagles or even abstract bird shapes.

Origin of the Name

The name “souzu” comes from the Chinese term for the rope or string used to bind ancient Chinese coins. While pinzu represents the coins themselves, souzu represents the bound rolls, bamboo rods threaded through the holes in stacked coins, creating the rope-bound currency stacks of historical China.

So the three suits together tell a complete currency story: pinzu (coins), souzu (rope-bound stacks of coins), and manzu (the highest currency unit, ten thousand). This origin is why the three suits are often described as different denominations of money in older mahjong texts.

Souzu in Riichi Strategy

Souzu plays identically to manzu and pinzu in riichi rules. All yaku apply equally, and the choice of which suit to concentrate in is purely preference. Where souzu has a unique strategic dimension is its connection to the yakuman ryuuiisou (all green), a hand made entirely of green tiles, which only includes 2-souzu, 3-souzu, 4-souzu, 6-souzu, 8-souzu, and the green dragon (hatsu).

Ryuuiisou is one of the rarer yakuman because it requires precise tile commitment. If you find yourself with a heavy concentration of those specific green-colored souzu tiles plus a hatsu, the yakuman path opens up.

Souzu’s 1 and 9 are terminal tiles like all other suits, contributing to:

• Tanyao disqualification (if 1-souzu or 9-souzu appear)
• Junchan and chanta (yaku requiring terminals)
• Honroutou (only 1-souzu and 9-souzu qualify)

Souzu Notation

Mahjong notation uses s for souzu. So “1s” means 1 of souzu, “5s” means 5 of souzu, and “234s” means a 2-3-4 sequence in souzu. A typical hand notation: 123m 234s 678p 99p 5s 6s 7s reads as 1-2-3 manzu, 2-3-4 souzu, 6-7-8 pinzu, pair of 9-pin, plus 5-6-7 souzu.

Souzu in practice

You hold these tiles: 2s, 3s, 4s, 6s, 8s, 4s, 6s, 8s, hatsu (green dragon), hatsu, hatsu, 1m, 9m. You have a strong souzu green concentration plus a complete hatsu triplet. The 1m and 9m are your weakest tiles. By discarding them and pulling more 2s/3s/4s/6s/8s plus another hatsu pair, you’re working toward ryuuiisou, one of the rarest yakuman in riichi. The doubled 4s, 6s, and 8s must each grow into triplets or serve as the pair (only 2-3-4 sou can be a run in an all-green hand), and with the hatsu triplet the yakuman shape comes together.