Tedashi and tsumogiri

Tedashi and tsumogiri are terms that describe where in the hand a tile was discarded:

• Tedashi means to discard a tile that was already in the hand before the draw, i.e. any tile other than the just-drawn tile.
• Tsumogiri means to discard the just-drawn tile.

Reading opponent's tedashi and tsumogiri discards can be useful, as they can indicate what shapes are likely/unlikely to be in their hand. They are typically combined with other discard reading strategies.

When playing with physical tiles, players will have to manually keep track of discards. In online clients, it will vary. Notably, tenhou.net and Mahjong Soul have animations to display tedashi/tsumogiri when a tile is discarded, but have no indicator after the discard (forcing players to memorize the status of each desired tile).

Strategy

Learning to discard read

• Beginners do not need to worry about discard reading - other things like tile efficiency are far more important at this stage.
  • Being able to build hands efficiently is required for effective discard reading; discard reading requires knowing how players normally build their hands.
  • Other beginners tend to not build hands in a consistent way, lowering the effectiveness of discard reading.
• It is not required to memorize every single tile (e.g., if a guest wind is discarded turn 2, it doesn't matter if it's tedashi or tsumogiri). Try to focus on important tiles, such as dora and middle tiles, and tedashi discards after those tiles.

Discard reading

• Late tedashi, as well as tedashi after discarding a strong tile, tends to indicate an opponent has other tiles nearby. However, it doesn't guarantee that they will wait near said tile. E.g., late tedashi 3m might indicate they have a 34m ryanmen wait left, or a 345m complete sequence with a completely unrelated wait. Similarly, tedashi 5m -> tedashi 2m tends to indicate shapes around 2m.
• If an opponent tedashis a safe honor relatively late in the game, and there's no threat on the board, the opponent is likely in tenpai, or at least iishanten (where the honor was kept due to sakigiri).
• If an opponent tedashis a joint/pair (e.g. tedashi 3p 5p), they will likely wait on a better joint. Tedashi ryanmen usually means they have a ryanmen-or-better wait, or they are aiming for a yaku like honitsu or toitoi.

Karagiri

Karagiri is when a player tedashis another copy of a tile that they just drawn (e.g., have 3-sou in hand, draw a 3-sou, then discard the 3s in hand rather than the just drawn 3s).

Since karagiri gives out information about the hand, it should usually be avoided, though exceptions exist. The clearest example is to discard a 5 to accept a red 5. If it's all last and 1st place intentionally wants to deal in to end the game, you can karagiri to make your wait more obvious. It is possible to karagiri intending to mislead the opponent, however, since karagiri always gives out some amount of "true" information, this can be counterproductive.