A Variation can refer to a specific sequence of successive moves in a turn-based game, often used to specify a hypothetical future state of a game that is being played. Although the term is most commonly used in the context of Chess

Chess

Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

 analysis, it has been applied to other games. It also is a useful term used when describing computer tree

Game tree

In game theory, a game tree is a directed graph whose nodes are positions in a game and whose edges are moves. The complete game tree for a game is the game tree starting at the initial position and containing all possible moves from each position; the complete tree is the same tree as that...

-search algorithms (for example minimax) for playing games such as Go

Go (board game)

Go , is an ancient board game for two players that originated in China more than 2,000 years ago...

 or Chess

Chess

Chess is a two-player board game played on a chessboard, a square-checkered board with 64 squares arranged in an eight-by-eight grid. It is one of the world's most popular games, played by millions of people worldwide at home, in clubs, online, by correspondence, and in tournaments.Each player...

.

A variation can be any number of steps as long as each step would be legal if it were to be played. It is often as far ahead as a human or computer can calculate; or however long is necessary to reach a particular position of interest. It may also lead to a terminal state in the game, in which case the term "Winning Variation" or "Losing Variation" is sometimes used.

Principal variation

The principal variation refers to the particular variation that is the most advantageous to the current player, assuming each other player will respond with the move that best improves their own position. In other words, it is the "best" or "correct" line of play. In the context of tree

Game tree

In game theory, a game tree is a directed graph whose nodes are positions in a game and whose edges are moves. The complete game tree for a game is the game tree starting at the initial position and containing all possible moves from each position; the complete tree is the same tree as that...

-searching game Artificial Intelligence

Artificial intelligence

Artificial intelligence is the intelligence of machines and the branch of computer science that aims to create it. AI textbooks define the field as "the study and design of intelligent agents" where an intelligent agent is a system that perceives its environment and takes actions that maximize its...

 – in which this term is most common – it may also refer to the sequence of moves which is currently believed to be the most advantageous, but is not guaranteed due to the technical limitations of the algorithm.

See also

• Game tree
  Game tree
  In game theory, a game tree is a directed graph whose nodes are positions in a game and whose edges are moves. The complete game tree for a game is the game tree starting at the initial position and containing all possible moves from each position; the complete tree is the same tree as that...
  
  
• Backtracking
  Backtracking
  Backtracking is a general algorithm for finding all solutions to some computational problem, that incrementally builds candidates to the solutions, and abandons each partial candidate c as soon as it determines that c cannot possibly be completed to a valid solution.The classic textbook example...
  
  
• Minimax
  Minimax
  Minimax is a decision rule used in decision theory, game theory, statistics and philosophy for minimizing the possible loss for a worst case scenario. Alternatively, it can be thought of as maximizing the minimum gain...
  
  
• Negamax
  Negamax
  Negamax search is a slightly variant formulation of minimax search that relies on the zero-sum property of a two-player game.This algorithm heavily relies on the fact that max = -min to simplify the implementation of the minimax algorithm. More precisely, the value of a position to player A in such...
  
  
• Alpha-beta pruning
  Alpha-beta pruning
  Alpha-beta pruning is a search algorithm which seeks to decrease the number of nodes that are evaluated by the minimax algorithm in its search tree. It is an adversarial search algorithm used commonly for machine playing of two-player games...
  
  
• Negascout
  Negascout
  NegaScout or Principal Variation Search is a negamax algorithm that can be faster than alpha-beta pruning. Like alpha-beta pruning, NegaScout is a directional search algorithm for computing the minimax value of a node in a tree...