What is Koutsu (Triplet)?
Koutsu (刻子) is a combination of 3 identical tiles in mahjong. For example, 5-man 5-man 5-man (555m) or East-East-East are koutsu.
Koutsu is a type of set (mentsu) that can be made with both numbered tiles and honor tiles. The name comes from “刻” meaning “to carve/engrave,” referring to carving the same pattern three times.
Detailed Explanation of Koutsu
Types of Koutsu
| Type | Explanation | Example |
|---|---|---|
| Ankou (Concealed Set) | Triplet collected by yourself | Completed within hand |
| Minkou (Open Set) | Triplet made by calling pon | Uses opponent’s discard |
Examples of Koutsu
| Tile Type | Koutsu Examples |
|---|---|
| Man (Characters) | 111m, 555m, 999m |
| Pin (Circles) | 222p, 666p, 888p |
| Sou (Bamboos) | 333s, 777s, 999s |
| Honors | East-East-East, South-South-South, White-White-White, Red-Red-Red |
Difference Between Ankou and Minkou
| Aspect | Ankou | Minkou |
|---|---|---|
| Building Method | Collect 3 tiles yourself | Made by calling pon |
| Visibility | Hidden in hand | Exposed on table |
| Fu Calculation | Higher fu | Lower fu |
| Yaku Impact | Required for sanankou etc. | Some yaku won’t count |
Usage Examples
Real Game Situations
Example 1: Hand Explanation
"I made a triplet of red dragon, so that's 1 han confirmed"
"I have 2 concealed triplets, let me aim for sanankou"Example 2: Pon Decision
"I have 2 green dragons, let me call pon to make a triplet"
"I have a pair of dora, high score if I can pon"Example 3: Tactical Judgment
"Many triplets in hand, toitoi possibility"
"Let's play defensively with honor triplets"How to Build Koutsu
1. Collect by Yourself (Ankou)
- Advantages: Higher fu, maintains closed hand
- Disadvantages: Low probability, takes time
- Probability: About 11% chance to upgrade a pair to triplet
2. Call Pon (Minkou)
- Advantages: Certain to make, fast
- Disadvantages: Breaks closed hand, hand becomes readable
- Best for: Yakuhai, dora tiles, etc.
Related Terms
- Mentsu: General term for 3-tile sets
- Shuntsu: 3 consecutive numbered tiles
- Kantsu: 4 identical tiles
- Toitsu: 2 identical tiles (pair)
- Pon: Call to make a triplet
Common Mistakes and Points to Note
Points Beginners Often Mistake
-
Confusion with Kantsu
- Koutsu is 3 tiles, kantsu is 4 tiles
- Even after kan, it counts as 1 set
-
Counting Concealed Sets
- Even with ron win, it’s still ankou
- Once you pon, it immediately becomes minkou
-
Yaku Requirements
- Toitoi: All sets must be triplets
- Sanankou: Need 3 concealed triplets
-
Fu Calculation Differences
- Ankou is double the fu of minkou
- Terminals and honors are doubled again
Yaku Using Koutsu
Yaku Requiring Koutsu
| Yaku Name | Required Koutsu | Difficulty |
|---|---|---|
| Toitoi (All Triplets) | 4 triplets | ★★☆ |
| Sanankou (3 Concealed) | 3 concealed triplets | ★★★ |
| Suuankou (4 Concealed) | 4 concealed triplets | Yakuman |
| Sankantsu (3 Quads) | 3 quads | ★★★ |
Yaku Compatible with Koutsu
- Yakuhai: Honor triplet for 1 han
- Honroutou: Only terminal/honor triplets
- Sanshoku Doukou: Same number triplet in 3 suits
Strategic Points
When to Aim for Koutsu
-
Many pairs in starting hand
- 4+ pairs suggests toitoi route
- Choice between toitoi and chiitoitsu
-
Have a yakuhai pair
- Guaranteed 1 han
- Yaku confirmed even when calling
-
Have a dora pair
- Can expect higher score
- Actively consider calling pon
Disadvantages of Koutsu
- Hard to make (low probability)
- Hand becomes heavy
- Defense weakens (when calling)
Conclusion
Koutsu is a simple composition of 3 identical tiles, but it’s harder to make than sequences. However, it’s an important element leading to high-scoring yaku like toitoi and sanankou. Beginners should start by turning yakuhai or dora pairs into triplets, gradually learning to build hands utilizing koutsu. Understanding the difference between ankou and minkou is also important for scoring.