Backgammon Dictionary

A checker that is presently part of a prime or a block but which has the prospect of being used later to make another point.

A hit that uses the numbers on both dice taken together.   Compare: Direct Hit.

An opportunity to hit an opposing blot using the numbers on both dice taken together; a combination shot.   Compare: Direct Shot.

A double offered while the cube is still in the center, as opposed to a redouble where the player making the double has possession of the cube.

The amount initially wagered in a game of backgammon (1). At the end of the game, this amount is multiplied by the final value of the doubling cube, and further multiplied by 2 if the win is a gammon or 3 if the win is a backgammon (2).

A term used to describe a situation where one player has relative freedom to build his position or attack the opponent as he chooses, while the other player is reduced to making forced plays and trying to stave off disaster. The first player is said to have the initiative.

Home board.

Home board.

A division of a tournament designed for players too strong for the novice division and who do not wish to compete in the open division.

A player of some experience who has begun to hone his skills; the level of play between novice and advanced.

A sixteenth-century game popular in England and other European countries, and probably backgammon (1)'s direct ancestor. Rolls of doubles are played just like any other roll, and there are no gammons or backgammons (2).  See: How to Play Irish.

A elimination event, usually with a large entry fee, in which only the winner and runner-up receive prize money.

The fact that an improvement in the opponent's position can make redoubling correct in a position in which the player on roll owns the cube and has one remaining chance to redouble.

[Named for Oswald Jacoby, who proposed the rule.]  A rule popular in money play which says that gammons and backgammons (2) count only as a single game if neither player has offered a double during the game. The Jacoby rule is not used in match play. The rule speeds up play by eliminating situations where a player avoids doubling so he can play on for a gammon. See post by Daniel Murphy.

A game once popular in France in which players start at diagonally opposite corners and move around the board in the same direction.  See: How to Play Jacquet.

A formula devised by Rick Janowski for estimating match equity (1) at a given score. If d is the difference in match score and t is the number of points (4) the trailing player has to go, then the probability of the leading player winning the match is .5 + .85_d_ / (t+6).  See also: Neil's Numbers and Turner's Formula.

A collection of formulas devised by Rick Janowski for estimating cubeful equity from cubeless equity. The basic formula for cubeful equity (between take points) is:

CF = CL\*(1 - x) + CE\*x

where CF is cubeful equity, CL is cubeless equity, CE is cubeful equity assuming all doubles are perfectly efficient, and x is a number between 0 and 1 that measures the cube efficiency. Typical values for x range from 0.55 to 0.8.   See also: Janowski's Takepoint Formula.

A formula devised by Rick Janowski for estimating your take point given your cubeless probability of winning the game. The basic takepoint formula is:

       2L - 1  
TP = -----------  
     2W + 2L + x

where TP is the cubeless equity of your take point, L is the average value of your cubeless losses (e.g., −1, if you can't lose a gammon), W is the average value of your cubeless wins (e.g., +1 if you can't win a gammon), and x is a number between 0 and 1 (typically 0.55 to 0.8) that measures cube efficiency. See Janowski's article, Take-Points in Money Games.

The first commercial neural-net backgammon program (1994) after TD-Gammon.   Website: Jellyfish Backgammon.

Potential for awkward rolls on a future turn.  See also: Double Jeopardy.