Definition of Book

What does the term "book" mean in the world of sports betting? What is meant by the term "book"?

In sports betting, a "book" is an entity that accepts bets on a sports event.

"Books" make money by accepting bets on both sides of a sporting event and charging a "vig". For instance, if two teams have the exact same odds of winning a game, you would need to bet $110 in order to win $100 back on either side. So, let's say that Person A bets $110 on Team A to win, while Person B bets $110 on Team B to win. The "book" will need to pay out $100 to the winner as well as returning the $110 bet of the winner. So, the book makes $10 as their fee. The goal of a sports book is to balance the bets so that there is the same amount of money to be won on both sides. In order to do this, a book must keep the odds set so that they induce an equal amount of action on all outcomes.

Books are especially popular in Europe, as gambling on sports is a daily part of life for many people. Things aren't so clear cut in the United States, however, as people need to travel to Las Vegas in order to legally put a wager down on a sporting event.