Editing Mahjong (section)

===Ineligibility to win or "furiten"===
Rule exclusive to Japanese mahjong. Otherwise known as "you fucked up" or "pay attention, moron." The furiten state means you can't win off of other players (ron), no matter what they discard/kan/pei, though you can still draw a winning tile yourself and go out that way (tsumo). Comes in two kinds, only one of which you'll commonly encounter in practice: if your current hand can win with a tile that you threw away earlier, you're furiten until you change your hand so that your winning tiles no longer overlap with your discards. In practice, that's usually incredibly difficult to do, so have fun.

The other kind is if you pass up an opportunity to complete your hand off of another's discard. Not win; this is important with open hands that will have yaku with one hand-completing tile but won't (and therefore can't call ron) with another. Declining ron this way (even if you couldn't actually call it as in the previous sentence) puts you in furiten till your next draw. If you pass up a winning tile while in riichi, however, you're in furiten for the rest of the round and fully deserve it.