Terms Worth Knowing

Casino lobbies and betting slips are full of words that assume you already know them. This glossary collects the words that recur across our articles, with short definitions written for adults who are just starting out. Where an article explains a term in depth, we link to it.

Costs and odds

• House edge. The average share of each stake that a casino game keeps over a very long run of play. It is the price of the game, not a prediction of any one session.
• Return to player (RTP). The slot equivalent of the house edge, expressed the other way round: the portion of total stakes a game is built to hand back across an enormous number of spins.
• Margin, vig or juice. The cost a sportsbook builds into its prices. Convert every price in a market to a percentage and add them; anything above 100% is the margin.
• Implied probability. The chance a price suggests, before you remove the margin. With decimal odds it is 1 divided by the price.
• Decimal, fractional and American odds. Three ways of writing the same price. Decimal shows the total return per unit staked; fractional shows profit against stake; American shows profit on 100 or the stake needed for 100 profit.
• Commission. The fee a betting exchange takes from net winnings rather than pricing a margin into its odds.

Slot words

• Random number generator (RNG). The software that decides each spin's outcome independently of every spin before it.
• Volatility. How a slot's payouts are spread out. Calm games return small wins frequently; volatile ones can stay silent for a long while before a bigger payout.
• Payline. A pattern across the reels on which matching symbols pay.
• Free spins. Spins that do not cost the player a stake, triggered in a game or given as a promotion; promotional ones usually carry conditions.

Betting market words

• Moneyline. A bet on who wins, with no handicap.
• Point spread. A handicap that takes points from the favorite and gives them to the underdog. See what a point spread is.
• Over/under (total). A bet on whether the combined score lands above or below a line.
• Push. When the final figure equals the line exactly; the stake normally comes back.
• Hook. The half point added to a line so that a push cannot happen.
• Parlay. Several selections joined into one bet that only pays if all of them win.
• Backing and laying. On an exchange, betting that something will happen and betting that it will not.
• Liability. The amount a layer stands to lose if the outcome they laid comes in.
• In-play. Betting while an event is already under way, with prices updated constantly.

Account and terms words

• Wagering or play-through requirement. The turnover needed before promotional funds, or what they win, can be cashed out.
• Deposit limit. A cap you set on how much can be added to an account in a day, week or month.
• Cooling-off period. A pause of days or weeks you choose yourself, during which the account is locked.
• Self-exclusion. A longer block, chosen by the player, that closes the account for months or years.
• Sweepstakes coins. The redeemable virtual currency on a sweepstakes casino, kept separate from the play-only coins.

Understanding the words does not change the odds of any game. It does make it easier to see what a product costs and to spot an offer that sounds better than it is. Everything on this site is for adults, and the rules on gambling differ from place to place.