# Life and death

Life and death is a fundamental concept in the game of Go, where the status of a distinct group of stones, is determined as either being "alive", and may remain on the board, or "dead," where the group will be lost as "captured". The basic idea can be simply put that: A group must have two eyes (secured internal liberties) to live.

Life and death situations (or positions) occur when an area with stones is contained to a limited area by opponents stones, so as to make the status of that group questionable. Because the loss of a developed group can often mean the loss of the game, and because the efficient use of each move is important, knowing the life and death status of one's own groups (as well as one's opponent's) is an important skill to cultivate, if one is to become a strong player.

An example life and death situation:

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Go_position,_life_and_death,_1.png
This problem (Difficulty: 5 dan) begins with B1. Can white save his stones and "make life"? This kind of problem is called a semeai; where one is in a "race" to capture the opponent first...
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Go_position,_life_and_death,_2.png
W2 is the correct move here. Black approaches with B3, and white protects with W4. Note that both B and W groups have four liberties, and now it's Black's move...
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Go_position,_life_and_death,_3.png
After the next few moves, the situation becomes clearer. Despite black's best responses, the five white stones have one more liberty (the one below move 9) than black does. If it's not clear how white survives, see the next image for detail...
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Go_position,_life_and_death,_4.png
After W10, B11, W12, the black stones are in atari. When eventually black plays 13 (as a ko threat), white can capture the four black stones.

Virtually all games will have at least a few dead stones, and these are captured; an even game may have an equivalence of captures by both sides. And single stones and small groups are often sacrificed for tactical value, and these will factor in the scoring. But in cases where a group is more than of sacrificial value, that group must make life in order for one to have a chance at winning the overall game. Generally each side will have at most 4-5 living groups on the board at the end of the game. There is a go proverb that says that "Five groups may live, but the sixth will die" [1] (http://senseis.xmp.net/?path=GoProverbs&page=FiveGroupsMightLiveButTheSixthWillDie) which in a nutshell describes the need to emphasise connection between developing groups, so that the need for each to struggle for life is ameliorated by their connection. Since each group needs two eyes, (and eyes are sometimes hard to come by) the alternative is to connect out to another group, thereby sharing liberties.

## Aji

Even if a problem is lost, one can still use their own dead stones for aji (potential). For example in the alternate version below, though the white stones are considered "dead," white can still use each of his approach moves as ko threats.

Alternate version: Slight variations can make all the difference. For example if there was a black stone at /\, "B" would be a weakness, preventing the W atari at A: After W10 and B11 (at "B"), white must capture the stone at "B" before playing A. Black needs two approach moves to put white in atari at C, while White needs to take two moves just to capture "B", before playing A.

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