Editing Rules of Go (section)

=== Positions ===
'''Rule 4. At any time in the game, each intersection on the board is in one and only one of the following three states: 1) empty; 2) occupied by a black stone; or 3) occupied by a white stone. A ''position'' consists of an indication of the state of each intersection.'''

Specifying a position involves only the current state of the board. It requires no indication of whose turn it is, nor any information relating to previous moves or states of the board. This definition of "position" is used in Rule 8 ("positional superko").

The diagram shows a possible position:

{{Go board 5x5
| ul|  b|  u|  u|  b
|  b|  b|   |  w|  b
|  l|   |  w|   |  r
|  w|   |  w|  b|  w
| dl|  b|  w|  w| dr|24}}

Naturally, two stones are said to be ''adjacent'' if they occupy adjacent intersections. Similarly, a stone and an intersection are ''adjacent'' if the stone occupies an intersection adjacent to that intersection.

==== Connected stones and points ====
'''Definition. Two placed stones of the same color (or two empty intersections) are said to be connected if it is possible to draw a path from one to the other by passing only through adjacent intersections of the same state (empty, occupied by white, or occupied by black).'''

The concept of connected stones is used to describe (via the concept of ''liberties'', defined below) the conditions in which stones are ''captured'' by a move. The concept of connected empty points is used only at the end of the game, to define a player's ''score''.

In the following position, the stones 1 and 7 are connected by the sequence of black stones 1, 2, ..., 7, in which each stone (other than 1) is adjacent to the stone before it. The empty points ''a'' and ''k'' are connected by the sequence of empty points ''a'', ''b'', ..., ''k'', in which each point (other than ''a'') is adjacent to the one before it. In fact, it is easy to see in this position that all the black stones are connected to each other and that all the empty points are connected to each other.

{{Go board 5x5
|ul|  u|  u|  u| ur
|lK|  J|  I|  H| rG
| l| b4| b5| b6| rF
| l| b3|  A| b7| rE
|b1| b2| dB| dC|drD|24}}

The following position can be used as an example for when stones and empty points are connected.

{{Go board 5x5
|ulA| b1| uF| uF| b4
| b1| b1|  F| w8| b4
| lB|  B| w6|  E| rE
| w5|  B| w6| b3| w7
|dlC| b2| w6| w6|drD|24}}

In the diagram, stones and empty points are marked with the same number or letter, respectively, whenever they are connected to each other.

A ''chain'' is a set of one or more stones (necessarily of the same color) that are all connected to each other and that are not connected to any other stones. Although it is not necessary to define the word ''chain'' in order to state the rules, the concept is important for an understanding of the game.

For example, Black and White each have four chains in the diagram above. Black has one three-stone chain, one two-stone chain, and two one-stone chains. White has one four-stone chain and three one-stone chains.

It follows from the definitions that any stone on the board belongs to exactly one chain. Furthermore, saying that two distinct stones of the same color are connected is the same as saying that they belong to the same chain.

==== Liberties ====
'''In a given position, a ''liberty'' of a stone is an empty intersection adjacent to that stone or adjacent to a stone which is connected to that stone.'''

For example:

{{Go board 5x5
| ul|  u| uD|  w|urC
|  l|  E| b4|  b| b3
|  w| b5|  b| b2| rB
|  w|  w| b1|  w|  r
| dl|  w| dA|  d| dr|24}}

In the above position, the points ''a'', ''b'', ''c'', ''d'', ''e'', are the liberties of the black stone at 1.
* ''a'' is a liberty of Black 1 because it is adjacent to Black 1 itself.
* ''b'' is a liberty of Black 1 because it is adjacent to Black 2, which is connected to Black 1. Alternatively, ''b'' is adjacent to Black 3.
* ''c'' is a liberty of Black 1 because it is adjacent to Black 3, which is connected to Black 1.
* ''d'' is a liberty of Black 1 because it is adjacent to Black 4, which is connected to Black 1.
* ''e'' is a liberty of Black 1 because it is adjacent to Black 5, which is connected to Black 1. Alternatively, ''e'' is adjacent to Black 4.

The results are the same when determining the liberties of Black 2, or of any other stone belonging to the black chain.

{{Go board 5x5
| ul|  u| uF| w7|urE
| lA|  G| b2| b2| b2
| w4| b3|  H| w6| rD
| w4| w4| b1| b1| b1
|dlB| w4| dC| w5| b1|24}}

In this position:
* The black stones marked 1 have the liberties ''c'', ''d'' and ''h''.
* The black stones marked 2 have the liberties ''d'', ''e'', ''f'', ''g'' and ''h''. 
* The black stone marked 3 has the liberties ''g'' and ''h''.
* The white stones marked 4 have the liberties ''a'', ''b'' and ''c''.
* The white stone marked 5 has the single liberty ''c''.
* The white stone marked 6 has the liberties ''d'' and ''h''.
* The white stone marked 7 has the liberties ''e'' and ''f''.

Since the liberties of any two stones belonging to the same chain are identical, they are often called the ''liberties'' of that chain. For example, in the first diagram, the points ''a'', ''b'', ''c'', ''d'' and ''e'' are the liberties of the lone black chain. In the second diagram, the liberties of the black chain in the lower right are ''c'', ''d'' and ''h''.