USA · Guide
Prediction market, betting & casino glossary
A plain-English glossary of the terms used on US prediction markets, sportsbooks and online casinos. Each definition stands on its own, with links to the guides that go deeper.
Key takeaways
- An event contract pays a fixed amount (usually $1) if a yes/no event happens, so its price works like a probability.
- Prediction markets in the US are overseen by the CFTC; sportsbooks and online casinos by state gaming regulators.
- Odds can be written as American (+150), decimal (2.50) or fractional (3/2) — they all describe the same price.
- RTP and house edge are two sides of the same number: a 96% RTP game has a 4% house edge.
- Wagering (playthrough) requirements decide what a casino bonus is really worth.
Use this glossary alongside our ranking of the best US prediction markets and our ranking of the best US online casinos. Terms are grouped by topic and listed alphabetically within each group.
Prediction markets
Ask
The lowest price at which someone is currently willing to sell a contract. If the ask for “Yes” is 55¢, you can buy immediately at 55¢.
Bid
The highest price at which someone is currently willing to buy a contract. If you sell immediately, you get the bid.
Binary contract
A contract with only two outcomes: it pays a fixed amount (usually $1) if the event happens and nothing if it doesn’t. Most US event contracts are binary.
Combo
A single position that combines several outcomes, all of which must happen for it to pay — the prediction-market version of a parlay. Some platforms offer combos on sports.
Event contract
A financial contract whose payout depends on whether a specific event happens, such as “Will the Fed cut rates in December?” In the US, event contracts are listed on exchanges regulated by the CFTC. See how prediction markets work.
Implied probability
The chance of an outcome that a price represents. On a $1 binary contract, the price in cents is roughly the implied probability: 30¢ ≈ 30%.
Limit order
An order to buy or sell only at a price you choose, or better. It waits in the order book until someone takes it, which usually means paying lower fees than a market order.
Liquidity
How easily you can buy or sell without moving the price. Liquid markets have many orders close to the current price and a narrow spread.
Maker and taker
A maker adds an order to the order book (a limit order that isn’t filled right away); a taker fills an existing order. Some platforms charge takers more than makers.
Market order
An order to buy or sell immediately at the best available price. Fast, but in thin markets you may pay more than the last traded price.
Order book
The live list of all open buy and sell orders for a contract, sorted by price.
Prediction market
An exchange where people trade contracts on the outcome of future events. Prices move with supply and demand and can be read as the crowd’s estimate of each outcome’s probability. See our ranking of the best prediction markets in the US.
Resolution (settlement)
The moment a contract’s outcome is decided and winning contracts pay out. Each contract names its resolution source, such as an official government statistic or the final score.
Spread
The gap between the bid and the ask. A wide spread is a hidden cost: you buy high and sell low.
Yes and No shares
The two sides of a binary contract. A Yes share pays $1 if the event happens; a No share pays $1 if it doesn’t. Their prices add up to about $1.
Odds and sports betting
American odds
The odds format used by US sportsbooks. +150 means a $100 bet wins $150 in profit; -110 means you must bet $110 to win $100. Convert any format with our odds calculator.
Closing line
The final odds before a game starts. Consistently getting better odds than the closing line is widely seen as a sign of a skilled bettor.
Decimal odds
Odds written as the total return per $1 staked, including the stake. 2.50 returns $2.50 for every $1, a profit of $1.50.
Expected value (EV)
The average amount a bet wins or loses per play over the long run. A +EV bet is priced better than its true probability. Learn how in our expected value guide, or calculate it with our EV calculator.
Fractional odds
Odds written as profit over stake, common in the UK: 3/2 means you win $3 for every $2 staked.
Moneyline
A bet on which team or fighter wins, with no point spread.
Parlay
A single bet that combines several selections; all must win for the parlay to pay. Payouts are high because the odds multiply. See our parlay calculator.
Point spread
A handicap that makes an uneven game even for betting purposes. Chiefs -2.5 means the Chiefs must win by 3 or more for the bet to win.
Push
A result that lands exactly on the line (for example, a team wins by exactly the spread). The stake is returned.
Total (over/under)
A bet on whether the combined score of a game will be over or under a number set by the sportsbook.
Vig (vigorish, juice)
The margin a sportsbook builds into its odds. At -110 on both sides of a game, the book collects more than it pays out, whichever side wins.
Online casinos
Bonus spins
Free spins on selected slots given as a promotion. Winnings are usually paid as bonus money with wagering requirements.
Game weighting (contribution)
How much a bet on a given game counts toward a bonus wagering requirement. Slots often count 100%; table games may count 20% or less.
House edge
The average percentage of each wager a casino game keeps over the long run. It’s the flip side of RTP: a game with a 96% RTP has a 4% house edge. See RTP and house edge explained.
Live dealer
Table games such as blackjack or roulette streamed from a studio with a real dealer, played through an app or browser.
Lossback
A promotion that refunds some of your net losses over a set period, usually as bonus money or site credit with wagering requirements.
No-deposit bonus
A small bonus you get for signing up, without depositing. It almost always carries wagering requirements and a cap on what you can withdraw.
Progressive jackpot
A jackpot that grows with every bet placed on a linked group of games until someone wins it.
RTP (return to player)
The share of all money wagered on a game that it pays back to players over a very large number of plays. A 96% RTP means the game returns $96 per $100 wagered on average. It doesn’t predict any single session.
Site credit (bonus money)
Money that can be used to play but not withdrawn until its wagering requirement is met. Different casinos use different names for it.
Sweepstakes casino
A casino-style site that uses virtual currencies and prize “sweepstakes” instead of real-money wagering. Several states have banned them. See sweepstakes casinos explained.
Volatility
How much a game’s results swing. High-volatility slots pay less often but in bigger amounts; low-volatility slots pay small wins more often. Volatility doesn’t change the house edge.
Wagering (playthrough) requirement
How much you must bet before bonus money turns into withdrawable cash. A $100 bonus with 10x wagering requires $1,000 in bets. See casino bonuses explained.
Welcome bonus
A promotion for new customers, such as a deposit match, a lossback or bonus spins. Its real value depends on its terms.
Regulation and taxes
CFTC (Commodity Futures Trading Commission)
The federal agency that regulates US futures, options and swaps markets — including exchanges that list event contracts. See are prediction markets legal in the US?
DCM (designated contract market)
An exchange approved by the CFTC to list futures and other contracts, including event contracts. Kalshi and several other prediction markets operate DCMs.
DCO (derivatives clearing organization)
A CFTC-registered clearinghouse that stands between buyers and sellers, guaranteeing that trades settle.
FCM (futures commission merchant)
A CFTC-registered broker that accepts customer money for trading futures and similar contracts. Some prediction market apps, such as brokerage apps, reach exchanges through an FCM.
Geolocation
Technology licensed casinos and sportsbooks use to confirm you are physically inside a state where they may legally accept your wager.
iGaming
Industry term for regulated online casino games (slots, table games, live dealer), as distinct from sports betting.
KYC (know your customer)
The identity checks regulated platforms must run before you can deposit or trade, usually a name, date of birth, address and the last four digits of a Social Security number.
Self-certification
The process by which a CFTC-regulated exchange lists a new contract by certifying to the CFTC that it complies with the law, rather than waiting for approval. The CFTC can review and challenge a listing.
Self-exclusion
A voluntary program that blocks you from gambling for a set period, either with one operator or across every licensed operator in a state. See our responsible gambling guide.
State gaming regulator
The state agency that licenses and supervises casinos and sportsbooks, such as the New Jersey Division of Gaming Enforcement or the Pennsylvania Gaming Control Board.
W-2G
The IRS form a casino or sportsbook issues for certain large gambling wins, reporting them to you and to the IRS. See gambling and prediction market taxes.
Where to go next
- New to event contracts? Start with how prediction markets work, then compare the best prediction markets in the US.
- Looking for a casino? Check where online casinos are legal and our top 5 online casinos.
Frequently asked questions
What is the difference between a prediction market and a sportsbook?
A sportsbook sets the odds and takes the other side of your bet. A prediction market is an exchange where traders buy and sell contracts with each other, and the platform earns a fee. See prediction markets vs sportsbooks.
What does a price of 62¢ mean on a prediction market?
It means the market puts the chance of the event at roughly 62%. The contract pays $1 if the event happens, so you'd pay 62¢ to potentially receive $1, before fees.
Is RTP the same as my chance of winning?
No. RTP (return to player) is the share of all money wagered on a game that it pays back over a very large number of plays. It says nothing about any single session, which can end far above or below it.