Four-ball is a carom billiards game. The game is played on a pocketless table with four balls, usually one light red, one dark red, and two whites (or just two reds and two whites). 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 both red balls. The shooter is penalized a point for failure to carom on either red ball or if the shooter causes his cue ball to carom off the opponent's cue ball. Thus, the shooter must avoid any carom or kiss off of the opponent's ball while striving to carom on the two red object balls. A carom on only one red ball results in no points but ends the shooter's inning.
There are a few variations 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 game commences by hitting the red ball on the opposite side of the table (as in carom billiards), the players work their way down from their respective handicaps, and after having scored the final point a win is secured by doing a three-cushion shot. 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, and the game is over when the first player reaches the agreed-upon score.
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, one point shot and 10 points shot is doubled by hitting a cushion before hitting any of the other balls for a total of 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.