1. Objective
Riichi is the Japanese variant of Mahjong. The structure is the same as classic (four melds plus a pair), but a winning hand must contain at least one yaku (a recognized pattern) — you cannot win with a "naked" hand.
Dora (bonus tiles) add value but do not count as yaku, so beginners should memorize a few easy yaku first: tanyao (no terminals/honors), yakuhai (dragon or wind triplets), and riichi itself.
2. The tiles
Riichi uses the same 136 tiles as classic Mahjong. Terminals (1 and 9) and honor tiles (winds and dragons) are called 幺九牌 (yaochuu); avoiding them entirely is the tanyao yaku.
3. Game flow
Players draw and discard in turns. Calling a discard (chi/pon/kan) opens your hand — open hands cannot declare riichi and lose some yaku, so calls are a strategic trade-off.
The wall is drawn down to the last 14 tiles (the dead wall / kan wall). When no one wins, the hand is an exhaustive draw and the game moves to the next round.
4. Riichi
Riichi is a declaration made on your discard when your concealed hand is one tile away from winning (tenpai) and you have never called. You place a 1000-point stick and lock your hand.
After riichi you may only discard the tiles you draw — you cannot change your hand. Riichi itself is worth 1 han and gives you access to bonus points (ippatsu, ura-dora).
After declaring riichi you can still win: when another player discards one of your winning tiles you may ron, and you may always tsumo. But your hand is locked from then on — declare only when your wait is good (e.g. two-sided) and your points lead is safe.
5. Yaku (winning patterns)
Common yaku: riichi (1), tanyao (1, no terminals/honors), yakuhai (1, dragon or seat/round wind triplet), pinfu (1, all sequences, non-honor pair), iipeiko (1, two identical sequences), sanshoku (2, same sequence in all three suits), chiitoitsu (2, seven pairs), honitsu (3, one suit plus honors), chinitsu (6, one suit only).
Yakuman (13+ han) hands: kokushi musou (thirteen orphans), suuankou (four concealed triplets), daisangen (three dragon triplets) and more.
6. Furiten
Furiten is the most important defensive rule: if any of your winning tiles is among your own discards, you cannot win off another player's discard (only by self-draw).
Always check your discards before calling ron — declaring a win while furiten is a serious mistake in real play.
7. Quick reference
Quick reference: riichi = declare when concealed + tenpai (1000-pt stick), yaku required to win, dora adds han but is not a yaku, furiten blocks ron on discarded tiles you need.