What is Suji? Meaning, Reading Methods, and Safety Explained for Beginners

What is Suji (Intervals)?

Suji (筋) refers to tile combinations related to ryanmen waits in mahjong. Specifically, it indicates relationships of “1-4-7,” “2-5-8,” and “3-6-9,” which is an important theory for reading opponent waits during defense.

For example, if is discarded, the ryanmen waits (waiting ) and (waiting ) are negated, making and relatively safe.

Detailed Explanation of Suji

Six Types of Suji

Suji name	Tile combination	Center tile
1-4-7	1・4・7	4
2-5-8	2・5・8	5
3-6-9	3・6・9	6

※Exists for man, pin, and sou

Suji Principle

When :4m: is discarded:
- :2m::3m: ryanmen → waiting :1m::4m: (won't deal in on :4m:)
- :5m::6m: ryanmen → waiting :4m::7m: (won't deal in on :4m:)

Conclusion: :1m: and :7m: won't deal in on ryanmen wait

Suji Safety Levels

Suji type	Safety	Reason
Ryansuji (both)	High	Suji from both sides
Katasuji (one side)	Medium	Suji from one side only
Musuji (none)	Low	No suji

Usage Examples

Real Game Situations

Example 1: Using in Defense

":4m: was discarded, so :1m::7m: is suji"
"Riichi on :5p:, so :2p::8p: is suji"

Example 2: Safety Judgment

"This :3s: is musuji, so dangerous"
":6m: is ryansuji, relatively safe"

Example 3: Suji Reading Limitations

"Thought it was suji but dealt in..."
"Relying on suji is risky, genbutsu is certain"

Types and Reading of Suji

Omote-suji (Front Suji)

Most basic suji:

Read from riichi declaration tile
Read from discards
Highest reliability

Ura-suji (Back Suji)

When :4m: is discarded:
Front suji: :1m::7m:
Back suji: :2m::5m: (conversely dangerous)

Aida Yonken (Between Four)

When :1m: and :5m: are discarded:
→ :2m::3m::4m: relatively safe

Genbutsu: 100% safe tiles
Kabe: Reading from 4 visible tiles
Betaori: Complete fold defense
Musuji: Tiles without suji
Ryanmen Machi: Wait underlying suji

Common Mistakes and Points to Note

Points Beginners Often Mistake

Overreliance on suji
- Suji is not 100% safe
- Ineffective against kanchan, penchan, tanki
Back suji danger
- Opposite of front suji is dangerous
- Especially early discards
Pre-riichi suji
- Suji from pre-riichi discards invalid
- Calculate from after riichi
Miscounting suji
- 1-4-7, 2-5-8, 3-6-9
- Easy to mistake until familiar

Defense Tactics Using Suji

Defense Priority

Genbutsu (100% safe)
Honors (especially fresh honor tiles)
Suji (ryansuji > katasuji)
Terminals (1・9)
Musuji (most dangerous)

Suji Reliability

Situation	Reliability	Reason
Early game suji	Low	Hand still fluid
Riichi tile suji	High	High ryanmen possibility
Late game suji	Medium	Bad waits increase

Waits Where Suji Doesn’t Work

Suji Theory Limitations

Wait type	Suji effectiveness
Ryanmen machi	◎ (Effective)
Kanchan machi	× (Ineffective)
Penchan machi	× (Ineffective)
Tanki machi	× (Ineffective)
Shanpon machi	× (Ineffective)

Advanced Suji Techniques

Morohikkake (Double Trap)

Riichi player discarded :5m:
→ Normally :2m::8m: is safe suji
→ But waiting :4m::7m: (targeting :8m:)

Detecting Suji Traps

Early riichi often honest ryanmen
Late riichi may be irregular waits
Read discard flow

Suji Statistics

Suji Safety Data

Ryansuji safety: About 85%
Katasuji safety: About 70%
Musuji danger: About 40% are winning tiles

Conclusion

Suji is a defensive theory based on ryanmen waits, a fundamental technique for reading opponent waits. Understanding the 1-4-7, 2-5-8, 3-6-9 relationships allows inferring safe tiles from discards. However, suji is not 100% safe and doesn’t work against kanchan or tanki waits. Beginners should learn the suji basics and use them combined with genbutsu for safer defense.