Juice is the fee a bookmaker or casino takes for letting you play. It goes by plenty of other names: vigorish, vig, under-juice, the cut, the take and the margin.
In sports betting, juice is built into the odds. A standard two-way line at −110 on each side means risking 110 to win 100, so the book profits whichever side wins if the money is balanced. In a poker room, where players compete against each other and the house cannot win a hand, juice is collected in other ways. The room takes a small cut of each pot, may charge only once a hand reaches the flop, or bills players per half-hour or hour at the table. Baccarat’s commission on winning banker bets is another example. For operators, margin settings are among the most important commercial levers in a sportsbook or poker product.