Backgammon Glossary Dictionary: E

Early Game: The first few moves of a game, before the players have settled on a particular game plan.
Early-Late Ratio: A comparison of the cost of doubling slightly before opponent’s drop point versus doubling slightly past opponent’s drop point. This number varies depending on the score of the match, the level of the cube, and the chance of gammon in the current game. It is useful in determining how aggressively a player should double to avoid losing his market. See post by Tom Keith.
Edge of a Prime: The open point directly in front of a prime.

Effective Pip Count

The average number of rolls required to bear off all your checkers multiplied by the average pip value of a roll (49/6 pips). A player’s EPC is equal to his actual pip count plus the wastage of the position. For more information, see article by Walter Trice and post by Douglas Zare.
Efficient Double: A double made at its point of maximum effectiveness, when the opponent would be correct to either accept or refuse.
Eject: To abandon an ace-point game to avoid losing a backgammon or a gammon.
Elimination Format: A tournament event in which half the competitors are eliminated each round until just one player remains. Compare: Round Robin Format.

Elo Ratings System

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.
EMG Equity: Equivalent-to-money-game equity.
End Game: The phase of a game which starts when either player begins to bear off.
Enter: 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.
EPC: Effective pip count.
Equity: 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.
Equivalent-to-Money-Game 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.
Error Rate: 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.
Escape: To advance a runner to safety or past the opponent’s blockade.
Establish a Point: Make a point.
Eureka: [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.
Exposed Checker: A blot within range of a direct hit.
Extras: See: Mandatory Extras.

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