[Glossary of Mahjong Terms #8] Mahjong Tactical Terms

By TAKEYuichi

October 27, 2025 3 min read

Mahjong Tactical Terms & Suji Logic

Defense wins games in Riichi mahjong—and that defense often begins with suji: reading safe versus dangerous tiles from discards. This guide explains the core suji families and the practical tactics used to fold, push, and maneuver safely.

1. Suji Logic (スジ系用語)

筋 / Suji（両面待ちライン）: A “line” formed by an open-ended block (塔子 / taatsu) that would complete a sequence if one outer tile arrives. Example: with 4–5 in hand, the wait is 3–6. The six basic suji pairs are: 1–4, 2–5, 3–6, 4–7, 5–8, 6–9. theory
表筋 / Omote-suji: “Front suji” considered relatively safer versus an opponent’s open-ended wait due to furiten logic based on their visible discards: a discarded 4 suggests no 1–4 nor 4–7; a 5 suggests no 2–5 nor 5–8; a 6 suggests no 3–6 nor 6–9. The corresponding safer suji are 1–7, 2–8, 3–9. defense
中筋 / Naka-suji: “Middle suji” safety reads: discarding 1 or 7 implies 4 is safer; 2 or 8 implies 5 is safer; 3 or 9 implies 6 is safer. defense
片筋 / Kata-suji: “Half suji” impacting only one side of an opponent’s potential open-ended wait. E.g., if 1 has been discarded, then 4 is partially safer; with 2 → 5, 3 → 6, 7 → 4, 8 → 5, 9 → 6. defense
裏筋 / Ura-suji: “Back suji” created from tiles adjacent to a discard—often dangerous because a player may shift from a closed wait to an open-ended wait. Examples from a discard: 1 → 2–5, 2 → 3–6, 3 → 4–7, 4 → 5–8, 5 → 1–4 & 6–9, 6 → 2–5, 7 → 3–6, 8 → 4–7, 9 → 5–8. danger
間四軒 / Aida-yonken: “Between four houses”: overlapping back-suji that double-confirm a dangerous line (e.g., discards of 1 and 6 both point to 2–5). Highly risky. danger
スジを追う / Follow the suji: Choosing discards according to suji safety to avoid dealing into open-ended waits. A core defensive habit. technique

2. Tactical Terms (戦術系用語)

オリる / Fold: Prioritizing safety against a tenpai or riichi opponent: discard safer tiles and avoid dangerous ones instead of pursuing your own win. defense
ベタオリ / Beta-ori: Full fold: give up winning entirely and discard only genbutsu (proven safe) or completely safe tiles; if none exist, infer safety via suji. Hand value/shape is sacrificed for survival. defense
ツッパる / Push: Continuing to attack even through risk—discarding potentially dangerous tiles to pursue your win. offense
ゼンツッパ（ゼンツ） / All-in Push: Committed aggression: keep pushing with risky discards until you win (or lose), prioritizing your hand completion over defense. offense
回し打ち / Mawashi-uchi: “Weave and wait”: rotate through safer discards to avoid ron while keeping your hand live to aim for a later win. balance
合わせ打ち / Awase-uchi: Discarding the same tile as the player immediately before you. That tile is “same-turn safe” (cannot be ron-called in that cycle). defense
スジ追い / Suji-chasing: Applying suji logic proactively to choose safer discards and avoid dangerous lines. technique
壁 / Kabe: “Wall”: all four copies of a number tile are visible on the table. This creates suji-based safe discards (“wall suji”) that cannot complete certain open-ended waits. defense
ノーチャンス / No-chance: Another term for a complete wall: with all four copies visible, the corresponding open-ended wait is impossible. defense
ワンチャンス / One-chance: Three copies of a number tile are visible; one remains. The classic open-ended wait using both copies is impossible, but a single-sided wait may still exist—use caution. defense
現物 / Genbutsu: Tiles proven safe against a specific opponent (already in their discard row, called set, or post-riichi discards). That opponent cannot ron on those tiles. defense
完全安全牌 / Completely Safe Tile: A tile that is safe against all opponents (e.g., appears in every player’s discards). Awase-uchi tiles are also completely safe, but only within the same turn cycle. defense
生牌 / Shonpai: A tile not yet visible anywhere (no one has discarded/exposed it, nor is it an indicator). Often considered risky, especially near riichi. risk

Tip: Combine suji with kabe, genbutsu, and read of opponents’ tendencies. Suji is a guide—not a guarantee. When multiple signals conflict, lean toward survival unless your hand’s value and win rate justify the push.