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In go, "seki" describes a position where neither player wants to play on certain points, because that would let the other player capture some of their stones. This usually results in two groups of stones being alive because neither one can be killed. Scoring can depend on the rules in use. Use this tag on questions about how to understand seki, interesting positions that are seki, but not usually to problems where seki is just one possibility.

In , "seki" describes a situation where neither player wants to play on certain points, because playing on those points would let the other player capture a group of their stones. This usually results in two groups of stones being alive because neither one can be killed.

Classic example

$$Bc Classic seki example
$$ +----------------
$$ | . O B a W X . .
$$ | . O B b W X . .
$$ | . O B B W X . .
$$ | . O O O X X . .
$$ | . . . . . . . .

The classic seki example is a situation like this one. Neither Black nor White can afford to play at points a or b, because that would reduce their marked group down to one liberty and let the other player capture it next turn. Since neither player will normally1 play a or b in this situation, both marked groups are alive, but neither player can claim this part of the board as their territory.

1But see the section on Seki and

Eyes and scoring

In some sekis the score depends on the rule set in force: both sides may have eyes of different sizes, and in this case Japanese rules do not count the eyes while Chinese and AGA Rules do:

$$Bc Seki with eyes
$$ +------------------------
$$ | . O B . B a W . . W X .
$$ | . O B B B B W W W W X .
$$ | . O O O O O X X X X X .
$$ | . . . . . . . . . . . .

In this case a play at a puts both marked chains in atari, allowing the opponent to capture.

$$Bc Seki with big difference in scoring
$$ +------------------------
$$ | . O X . X a O b X O O X .
$$ | . O X X X X O X B X O X .
$$ | . O O O O X O X X O O X .
$$ | . . . . O X O O O O X X .
$$ | . . . . O O X X X X X . .
$$ | . . . . . . . . . . . . .

In this seki (because of a) there is a big difference in the Japanese score (0 points) and the Chinese/AGA score (13 - 1 = 12 points net to White). Note that capturing at b does not make White a second eye if Black plays back at the marked stone, J18 (rabbitty six).

Seki and ko

As already stated, normally neither side will play in the seki. A possible exception is during a -fight when one player uses it as a ko-threat although it loses points. This is, roughly speaking, only a good move when it is necessary to win the ko and that gains more points than are lost in the seki.

See also

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