The d4 square is adjacent to c4, e4, d3, and d5. In Arimaa, adjacent does not include diagonals, which have no place in the rules.
The Arimaa Challenge was an annual match between a top bot and top human players; humans dominated for eleven years, until a bot's surprise victory in 2015.
An opponent's home trap: c6 and f6 are away traps for Gold, while c3 and f3 are away traps for Silver.
The second strongest of the six unique Arimaa pieces. Each side has one camel.
A captured piece is removed from the board; a piece is captured when it occupies a trap square with no friendly piece beside it. There are two common ways a piece might be captured: it could be dislodged into an undefended trap, or might already be on a defended trap square which then becomes undefended.
The fifth strongest of the six unique Arimaa pieces. Each side has two cats.
The fourth strongest of the six unique Arimaa pieces. Each side has two dogs.
Prior to July 1, 2008, one who had lost all eight rabbits could still get a draw by capturing all remaining enemy rabbits. Draws are no longer possible, as a game now ends when one side loses all eight rabbits.
A player wins by elimination if the opponent has no rabbits left. In the rare event that each player loses his last rabbit in the same move, the one who made the move wins. See also Goal, Immobilization.
An exchange or trade occurs when each side captures material within a few turns. If each side captures a rabbit, that is a rabbit exchange. If the gold camel is captured and then a silver horse is captured, that is a camel-for-horse exchange. See also Sacrifice.
A four-step move which can be undone in two steps by the opponent. Like three-for-ones, four-for-twos are seldom good moves.
A piece is frozen if no friendly piece occupies an adjacent square, and a stronger enemy piece does occupy one. A frozen piece cannot move until a friendly piece is beside it, or until the stronger enemy piece leaves.
A free piece can move around with limited risk. Blockades, frames, hostages, and goal threats may restrict pieces on both sides, leaving other pieces to decide the game. Having the strongest free piece or strongest local piece can be a large advantage.
The third strongest of the six unique Arimaa pieces. Each side has two horses.
A player wins by immobilization if the opponent has no piece which can move, or if any move the opponent could make would recreate a position they created twice before. See also Blockade, Goal, Elimination.
A square north, south, east, or west of a trap square.
Not recognizing a lost cause, some bots will go all out to save a doomed strong piece. The bot sends over a weak piece to defend it, only to have the weak piece captured with the strong piece no better off. The cycle may repeat several times, with the bot sending over lemmings and the opponent capturing them.
An elephant is said to be overloaded if its side faces multiple threats which no other piece can defend against. Other pieces might become overloaded first, causing a ripple effect.
A slow game in which the players are allowed a specified number of hours or days to complete each move. Historically postal games (e.g. chess, go) were played by old-fashioned mail and a single game could last for years. Nowadays, postal games are normally played online over a period of weeks or months. Also known as a correspondence game.
Pull and replace
A piece can push a weaker enemy piece by first moving it to an adjacent empty square, and then itself stepping onto the square which that enemy piece had occupied. A push requires two steps. A phalanx may block a push.
Push and replace
A quarter of the board (16 squares), distinguished by compass directions from the perspective of Gold. The northwest quadrant contains the c6 trap, the northeast contains f6, the southwest contains c3, and the southeast contains f3.
One of eight rows on an Arimaa board. Gold begins the game with 16 pieces on the first and second ranks, while Silver begins with 16 pieces on the seventh and eighth ranks. The home rank for Gold is 1, while Silver's is 8.
A player who has created the same position twice may never create that exact position again. This is a consideration in sequences where players undo each other's moves.
When a piece holding a blockade or frame is replaced by a weaker piece or a phalanx, the original piece has rotated out. If a hostage defender is replaced, usually by multiple weaker pieces, the original defender has rotated out. A piece can likewise rotate out of a trap control fight. See also Swarm.
A strong piece might be sacrificed so that a friendly rabbit can reach goal. A weak piece might be sacrificed while one secures a frame or hostage. Likewise, one might have to give up a piece to break an elephant blockade or stop an enemy goal.
There are six unique types of pieces, each with a different strength. A piece can push, pull, or freeze any weaker enemy piece. From strongest to weakest, the units are elephant, camel, horse, dog, cat, and rabbit.
The elephants, camels, and horses are sometimes known as strong pieces. When one side loses two such pieces, an opposing dog might then be considered a strong piece, as it faces threats from only two enemy pieces.
When a piece takes a step and then returns to its original square while pulling a piece, and the pulled piece is neither blocked nor frozen, those three steps can be undone in a single step by the opponent. If this in fact happens, those three steps gave away time.
Three steps which could be undone in three steps by the opponent. When three steps cancel three steps, both sides have effectively taken zero- or one-step turns. This may continue for several turns, as long as the fourth steps sometimes create unique positions.
There are four trap squares on the board, located at c3, c6, f3 and f6. A piece can be captured in a trap square.
A player completes a turn by moving pieces a total of one, two, three or four legal steps. The opposing player then gets a turn. Also known as a move.