Tsumo

Tsumo is winning by drawing the final tile of your hand yourself from the wall, as opposed to claiming a discard (ron). When you draw the tile that completes your waiting hand, you declare tsumo, reveal the hand, and collect from all opponents rather than from a single discarder. The word is Japanese, but self-draw wins exist across every mahjong variant.

The payment structure is what distinguishes tsumo. In riichi all three opponents pay: the dealer (or non-dealers, depending on who won) pays a larger share and the others pay smaller equal shares, and the rounded sums are slightly higher in total than the equivalent ron, so a self-draw is usually worth a bit more. In Hong Kong and many Chinese rules a self-draw similarly spreads payment across all losers, often with a bonus, whereas a discard win is paid mainly by the discarder.

A self-draw also carries scoring advantages beyond payment. In a closed hand, winning by tsumo grants the menzen tsumo yaku in riichi, meaning a concealed tenpai hand with no other yaku can still win by self-draw even though it could not win by ron. Self-draw also enables special yaku like haitei (winning on the very last tile of the wall) and rinshan kaihou (winning on the replacement tile after a kong). However, declaring riichi commits you, and an open hand gains no menzen tsumo.

For example, if your closed hand is tenpai waiting on 5p and you draw 5p from the live wall, you declare tsumo, score menzen tsumo plus any other yaku, and all three opponents split the payment, the dealer paying double the non-dealer share.