Alive - Introductory

  Difficulty: Introductory  

Like other people, go players use language in a loose, informal way. So it is with life and death. A group may be alive at one point in the game, but dead at the end, and vice versa.

There are groups that are absolutely alive, even if their owner always passes.

[Diagram]
Absolutely alive  

It would take two plays to capture the Black stones, but White cannot make even one play to do so, because trying to play on one of the circle points would leave a stone with no liberty, and that is not allowed. (Even if were, the stone would be removed before the next play.) The circle points are called eyes and groups with two eyes are alive.

When go players call a group alive, they often mean this kind of situation.

[Diagram]
Alive  

Black is alive, because

[Diagram]
Defense  

if White tries to kill Black's group, Black has a reply to save it. If W1, B2, and vice versa. Note that after B2, Black is absolutely alive.

[Diagram]
Seki  

Another way to live is in seki. The Black and White groups in the corner are in seki, mutually alive. If either side played a stone on the circle point, they would put both groups in atari, and the opponent could capture their whole group.

Groups in seki are not absolutely alive.

Sometimes whether a group lives or dies depends upon who has sente (see unsettled), and sometimes it depends upon a ko. Also, it is not always easy to tell whether a group is alive or dead. There is a whole class of life and death problems in go.

For more, see alive.


Alive - Introductory last edited by Dieter on November 30, 2011 - 18:33
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