Four-ball is a carom billiards game. The game is played on a pocketless table with four balls, usually two reds and two whites (in some sets, one of the white balls is yellow). Each player is assigned one of the white balls as a cue ball. A point is scored when a shooter caroms on any two other balls. Two points are scored when the player caroms on each of the three other balls.
A variant of four-ball is the East Asian game yotsudama (四つ球?, Japanese for "four balls") or sagu (사구, Korean for "four balls"). The game is played with two red object balls, one white cue ball and one yellow cue ball (or sometimes both cue balls are white, one having a red spot). Each of the two players is assigned his or her own cue ball. A point is scored when the shooter caroms on two balls. A carom on only one ball results in no points but ends the shooter's inning.
There are a few differences between the Korean and the Japanese variants. In the Korean version, the cue ball is placed beside one of the red object balls for the opening shot, and play commences by hitting the red ball on the opposite side of the table (as in carom billiards), whilst in the Japanese version, the cue ball is placed behind the second red object ball, and play commences by hitting the red object ball nearest to the cue ball. In the Korean version, after having scored the final point, a win is secured by doing a three-cushion shot, whilst in the Japanese version, the game is simply over when a player reaches the agreed-upon score. In the Korean version, a player is penalised a point if the cue ball caroms off the opponent's cue ball, whilst in the Japanese version, doing so is legal, as the opponent's cue ball is used as an object ball.
Central European version
A variation of four-ball is popular in Central Europe, especially in the Czech Republic. It is called desítkový karambol (Czech for "tenfold carom") and is played with two white balls, a blue ball, and a red ball which serves as the cue ball. Players score a point by hitting on any other two balls with the cue ball. A hit off all three balls, however, scores 10 points. The score is doubled by hitting a cushion before hitting any of the other balls for a total of either 2 or 20 points in one shot.
- Froeshcle, Robert (1971). Official Rule Book for All Pocket & Carom Billiard Games. Billiard Congress of America.
- Photo of yotsudama balls from a commercial supplier
- Photo of Czech balls from a commercial supplier
- Article (Japanese) explaining the differences between the Korean and Japanese variants, and with images showing the different placement of the balls for the opening shot
- Link to a Czech Republic source (Czech) explaining the rules of Czech four-ball
- The official website of the UK version of 4 Ball Billiards complete with explanation of rules and variations.