Backgammon Dictionary

A game popular in French high society prior to the Revolution. Players score points for making specific plays or moving their checkers into certain configurations.  See: How to Play Trictrac.

The French name for "backgammon."

Backgammon (2).

Traditional name for the three-point.

A rollout which is not played to the end of the game. Instead, the position is rolled out a given number of plies (the horizon of the rollout) and estimates of the equities of the resulting positions are averaged together. A truncated rollout has more systematic error than a full rollout but is faster because each trial is shorter, and a truncated rollout has less variance so fewer trials are required to converge on a result. See post by Gregg Cattanach.

The sequence of actions that each player takes in alternation. One turn consists of: (a) possibly offering a double; (b) rolling the dice; (c) playing the roll; and (d) picking up the dice.

A simple formula devised by Stephen Turner for estimating the match equity (1) at a given score. Expressed as a percent, the leader's match equity E = 50 + (24/T + 3) * D, where T is the number of points (4) the trailer still needs and D is the difference in scores.  Compare: Janowski's Formula and Neil's Numbers.

Move from the opponent's outer board to your own outer board.

To offer a double.

To offer a double.

A mode available in some backgammon-playing programs which allows the computer to evaluate your moves as you make them and alert you to any errors it thinks you made.

To offer a double.

The second point (1) in a player's home board, adjacent to the one-point; also called the deuce-point.

A bearoff database with the correct equity for each possible combination of two opposing bearoff positions. Four separate equities are recorded for each position: three cubeful equities (one for each state of the doubling cube), and one cubeless equity. A two-sided database is more accurate than a one-sided database, but requires considerably more room.

The player judged most likely to lose a game or match.  Compare: Favorite.

To make a safe, unnecessarily timid play when a stronger, more aggressive play is available.

A blot in the opponent's home board which is within direct range of three or more of the opponent's builders and therefore in danger of being pointed on.

A not-for-profit organization devoted to advancement of backgammon in the United States.   Website: usbgf.org.

Backgammon played using a doubling cube without any limit to the number of doubles and redoubles. Unlimited games are similar to money games, but are played without the Jacoby rule, beavers, or automatic doubles. In contrast, limited forms of backgammon include: match play and table stakes.

To remove checkers from a heavy point.

Level of random error in a rollout.