Life and death (死活) is a fundamental concept in the game of Go, where the status of a specific group of stones is determined as either being "alive", where they may remain on the board indefinitely, or "dead", where the group will be "captured" and removed from the board.
The basic idea can be summarized by: A group must have a means to evade capture -- forever -- by having at least two liberties that can't be filled at the same time (by having at least two "eyes") to sustain itself.The concept of life and death is a consequence of two basic Go rules.
This is often the wrong approach, and it is better to play generally to make a territory inside a group out of which two eyes can surely be made, if and when the opponent attacks it.
Groups with seven or more points of territory can usually form two eyes when attacked, unless there are structural weaknesses.
Because the loss of a group can 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.
Here alive, for example, is an unconditional judgement made, that with best play from both players, the group can survive to the end of the game.
That assumes the opponent starts: the alive status means that, whatever the attack made, there is an adequate defensive answer.
A group can be considered "alive", "dead", or "unsettled" based on whether two eyes can be made regardless of how the opponent plays.
Usually this will not be done during the game, but at the end, during calculation, the group will be labeled "dead" and removed as prisoners.
The unsettled shape is the four-stone pyramid, shown in the left bottom corner.
Whoever plays in the circled center spot gets the desired result, so the player whose move it is wins.
A two-by-two square space is dead: if black plays in the top left corner of the two-by-two square, white can respond by playing in the bottom right corner (see the L-shaped case in the previous section).
The opponent playing in the center point threatens to fill all but one spot with a bulky five shape, and there is no defense.
Any group surrounding more than six points is alive, but it may be necessary to respond correctly if the opponent attacks.
Additionally, because of special properties of the corner, a group with more than six points might not be unconditionally alive, as it is possible for the opponent to make an eye or two within its territory.
The black and white stones in contact with the circled points do not have any eyes and may seem dead.
Those dead stones are then removed, in an operation often called 'cleaning', which is a separate phase of the game.
Under Chinese rules, which use area counting, stones removed during the cleaning phase are returned to their bowls.
It is a novice mistake to carry out the capture of dead stones before it is of tactical importance to do so.
Expert players use a variety of 'squeezing' tactics, of which semedori, an advanced endgame technique, and shibori are two that have recognised Japanese-language names.