# Ari-ari — Riichi Mahjong Glossary

> A modern riichi mahjong rule set allowing both kuitan (open tanyao) and atozuke (winning with incomplete yaku).

**Source:** https://www.mahjongmaster.co/learn/riichi/glossary/ari-ari/
**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:** アリアリ
**Category:** rules
**Variant:** riichi

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## Ari-ari

**Ari-ari** (ありあり) is the most widely used rule set in modern riichi mahjong, characterized by permitting both kuitan (open tanyao) and atozuke (winning with an incomplete yaku). The term literally means "there is, there is," referring to the presence of these two allowances.

## Understanding Ari-ari

In riichi mahjong, players must form winning hands (agari) that contain at least one yaku (scoring pattern). However, different rule sets impose varying restrictions on which yaku are valid and under what conditions hands can be won.

### Kuitan Allowance

Kuitan (喰い断) refers to forming tanyao (all simples) through an open meld rather than a concealed hand. In ari-ari rules, this is permitted. This means a player can win with tanyao even if one or more melds are open (called, from the discard). Under stricter rule sets (nashi-nashi), kuitan is forbidden, requiring tanyao to be formed entirely from concealed tiles.

The allowance of kuitan significantly impacts hand selection strategy, as players can pursue tanyao more flexibly by calling tiles from opponents' discards rather than waiting for a fully concealed hand.

### Atozuke Allowance

Atozuke (後付け, literally "attach afterward") refers to completing a yaku only upon winning. In ari-ari rules, this is allowed. For example, a player might call tiles to form a hand that lacks a yaku at the moment of calling, but gains a yaku when the final winning tile is drawn or claimed. Common scenarios include:

- Drawing a tile that completes a yaku simultaneously with completing the hand structure
- Calling pon on a yakuhai pair with a shanpon wait, so the yaku only exists if you win on the honor tile
- Completing a yaku through the winning tile itself (such as forming a pair that completes a color sequence requirement)

In nashi-nashi rules, atozuke is forbidden; every yaku must be established before the winning tile is drawn.

## Strategic Impact

The ari-ari rule set opens significantly more winning possibilities compared to nashi-nashi rules. Players have greater flexibility in hand development, can pursue open melds more aggressively, and have more opportunities to win with minimal yaku. This makes ari-ari more accessible to casual players while maintaining strategic depth.

The rule set encourages faster gameplay and more frequent winning hands, making it popular in casual clubs, online platforms, and tournament play worldwide.

## Walking through Ari-ari

Consider a player with a hand containing 2-3-4 of bamboo (open meld), 5-6-7 of bamboo (open meld), 3-4-5 of dots (open meld), a pair of 5-characters, and 6-7 of characters waiting on 5 or 8 of characters. Upon winning, they score tanyao. This is valid under ari-ari rules because:

1. Kuitan is allowed, so tanyao formed with open melds is valid
2. Atozuke is allowed, so the yaku is established upon winning

Under nashi-nashi rules, this winning hand would be invalid.

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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/ari-ari/.*