# Suji — Riichi Mahjong Glossary

> Interval-based safe tile theory in mahjong. If an opponent discards a 4, tiles 1 and 7 become safer because they cannot form a ryanmen wait with 4.

**Source:** https://www.mahjongmaster.co/learn/riichi/glossary/suji/
**Author:** Kenji Tanaka (https://www.mahjongmaster.co/about/kenji-tanaka/)
**Publisher:** Mahjong Master (https://www.mahjongmaster.co)
**Published:** 2026-02-18
**Updated:** 2026-03-10
**Japanese:** 筋
**Category:** strategy
**Variant:** riichi

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# Suji

## What counts as Suji

**Suji** (筋) is an interval-based safe tile theory in mahjong that identifies tiles less likely to be needed by opponents based on their discard patterns. When a player discards a tile, certain other tiles become safer to play because they cannot form a ryanmen (two-sided) wait with the discarded tile.

## How Suji plays out at the table

Suji operates on a mathematical principle: tiles that are exactly three numbers apart from a discarded tile are safer because they cannot complete a ryanmen wait pattern with that tile.

### The Core Concept

In a numbered suit (1-9), a ryanmen wait is formed by two consecutive middle tiles, winning on either end. For example:
- A ryanmen wait on 3-4 requires either 2 or 5
- A ryanmen wait on 5-6 requires either 4 or 7

If an opponent discards a 4, they cannot be waiting on a ryanmen that includes 4. This means:
- They cannot hold a 2-3 ryanmen (it waits on 1 and 4)
- They cannot hold a 5-6 ryanmen (it waits on 4 and 7)

Therefore, tiles that are three numbers away from the discarded 4 become safer:
- **1** (three away: 4-3-2-1)
- **7** (three away: 4-5-6-7)

Edge tiles give one-sided suji: discard 1 → 4 safer; discard 2 → 5 safer; discard 3 → 6 safer. Only the middle discards (4, 5, 6) make two tiles safer at once.

### Practical Application

Suji is most reliable when:
- An opponent has already discarded the tile in question (they clearly don't need it)
- Multiple players have discarded from the same suji line
- The discard came early in the hand when the player's wait was already formed

Suji becomes less reliable when:
- The discard was forced or came late in the hand
- The opponent may have changed their wait pattern
- Dealing with honor tiles, which don't follow the same ryanmen logic

### Limitations

Suji is a probabilistic tool, not a guarantee. Opponents can still win on suji tiles through:
- Shanpon (pair wait) patterns
- Tanki (single tile wait)
- Kanchan (gap wait) patterns that don't involve ryanmen
- Changing their hand structure after the initial discard

## Seeing Suji in play

**Scenario:** In a riichi hand, your opponent discards a 5 early in the hand. Based on suji theory:
- The 2 becomes safer (5-4-3-2)
- The 8 becomes safer (5-6-7-8)

If you're deciding between discarding a 2, 5, or 8 while in a dangerous position, the 2 and 8 are theoretically safer choices than the 5. However, this doesn't mean they're completely safe, your opponent could still be waiting on them through other patterns.

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*This content is from [Mahjong Master](https://www.mahjongmaster.co), a free educational reference for riichi (Japanese) and American (NMJL) mahjong. When citing this page, please link to https://www.mahjongmaster.co/learn/riichi/glossary/suji/.*