Backgammon Dictionary

A double made at or near the point of maximum effectiveness, when the opponent would be correct to either accept or refuse.

To abandon an ace-point game to avoid losing a backgammon (2) or a gammon.

A tournament event in which half the competitors are eliminated each round until just one player remains.  Compare: Round Robin Format.

A method of rating players devised by Arpad Elo for the U.S. Chess Federation in 1960. Most backgammon ratings systems are based on Elo's method; for example, see FIBS rating formula.

Equivalent-to-money-game equity.

The phase of a game which starts when either player begins to bear off.

To move a checker from the bar to an open point in the opponent's home board according to a roll of the dice. When a player has a checker on the bar, this is his only legal move.

Effective pip count.

The value of a position to one of the players. Equity is the sum of the values of the possible outcomes from a given position with each value multiplied by its probability of occurrence. It is the same as the fair settlement value of the position. Your equity is the negative of your opponent's equity. See post by Gary Wong. Equity comes in different flavors.  See: Cubeless Equity, Cubeful Equity, Match Equity, and EMG Equity.

Cubeful equity normalized by transforming it linearly so that winning a single game at the current value of the cube is reported as +1 and losing a single game at the current value of the cube is reported as −1. EMG equity is commonly used in match play to compare the size of errors in different games. See the Snowie Support FAQ for a further description and an example.

ER stands for Error Rate. Playing ER backgammon means playing with a view to making the least errors from the outset rather than deliberately making suboptimal plays to steer the game toward a position that your opponent will misplay or doesn't understand.

A measure of the average equity lost per move due to errors in play. The lost equity can be measured either in match-winning chances or EMG equity. Different programs compute error rate differently: Snowie divides by the total number of moves and reports the rate in "millipoints per move." Gnu Backgammon divides by the number of unforced plays. See post by Gregg Cattanach.

To advance a runner to safety or past the opponent's blockade.

Make a point.

[Also spelled "Eureika".]  Simplified backgammon, in which each player starts with two checkers on his one, two, and three-point, and three checkers on his four, five, and six-point. See How to Play Eureika.

A blot within range of a direct hit.

See: Mandatory Extras.

A neural-net backgammon program introduced in 2009.   Website: eXtreme Gammon.

To fail to reenter after being hit; to dance.

Speed board.