Sports betting glossary

When a sportsbook reduces the maximum bet size on a customer's account due to perceived sharp betting patterns.

The odds format used by US sportsbooks, expressing favorites with negative numbers and underdogs with positive numbers.

A betting strategy where you place bets on all possible outcomes of an event across different sportsbooks, guaranteeing a profit because the combined implied probabilities are less than 100%.

The practice of managing the money you've allocated to sports betting — separate from living expenses — and sizing bets as a percentage of that bankroll rather than betting fixed dollar amounts.

A platform where bettors trade against each other rather than against a bookmaker. The exchange takes a commission (typically 2–5%) on winning bets but doesn't set lines or build vig into the odds. Novig, Betfair, and Sporttrade are major exchanges.

Promotional credit issued by sportsbooks that can be used to place a bet but doesn't return the stake on a winning wager.

Paying extra vig to move a spread or total in your favor by a small amount.

An option offered by some sportsbooks to close out a bet early, accepting a guaranteed payout in exchange for forgoing the original outcome.

The Commodity Futures Trading Commission — the US federal agency that regulates derivatives markets, including the prediction market exchanges that now offer sports event contracts. CFTC regulation operates independently of state gambling commissions, which is what allows platforms like Kalshi to operate nationwide.

A Las Vegas-based sportsbook that accepts large stakes from professional bettors, posts lines early, and rarely limits winning customers. One of the few US-regulated books with a genuinely sharp posture.

The final betting odds posted at a sportsbook just before an event begins.

The difference between the odds you bet at and the odds at the moment the game starts (the closing line). Positive CLV means you got a better price than the market's final estimate, which is the strongest short-term evidence of betting skill.

Winning a bet against the spread — the favored team wins by more than the spread, or the underdog loses by less than the spread (or wins outright).

The international odds format expressing total return per dollar staked, including the original stake.

The process of removing the sportsbook's vig from a set of odds to recover the implied true probability of each outcome. Performed by dividing each outcome's vig-included implied probability by the sum of all outcome probabilities, producing a normalized set that sums to 100%.

Platforms where users build entries combining multiple player picks against fixed lines, with payouts based on whether all picks hit.

The percentage gap between the true probability of an outcome and the implied probability from the odds you're being offered. A 5% edge means the offered odds underprice the true probability by 5 percentage points.

The average amount a bet wins or loses per dollar wagered over many repetitions. A bet has positive expected value (+EV) when the offered odds imply a lower probability than the true probability of the outcome.

The odds you'd see if a sportsbook charged zero vig — odds that exactly match the true probability of the outcome. Useful as a reference for measuring how much vig a book charges and for calculating expected value.

The traditional UK odds format expressing profit relative to stake as a fraction.

A bet on a long-term outcome decided over a season or tournament, like a championship winner or season-long award.

Placing additional bets to reduce or eliminate risk on an existing position, locking in guaranteed profit or limiting loss.

The percentage of total wagered that a sportsbook actually keeps as profit after all bets settle — distinct from the vig, which is what they charge in theory.

The probability that a set of odds suggests for an outcome. American odds of -150 imply 60% probability; +200 implies 33.3%. Implied probability includes the sportsbook's vig, so it's always slightly higher than the true probability.

A US-regulated prediction market exchange that trades binary contracts on event outcomes, including elections, economics, weather, and a growing roster of sports markets. Operates under CFTC oversight as a Designated Contract Market — the first federally regulated sports betting platform in the United States.

A bet sizing formula that maximizes long-term bankroll growth by betting a fraction of your bankroll proportional to your edge and the offered odds. Most bettors use a fractional Kelly (¼ or ½) to reduce variance.

A margin of victory that occurs disproportionately often in a sport, making lines that cross it especially valuable. In NFL, 3 (field goal) and 7 (touchdown) are the primary key numbers.

The identity verification process required by regulated sportsbooks and prediction markets before allowing betting or large transactions.

A bet against an outcome occurring, placed on a betting exchange. Functionally equivalent to taking the role of the bookmaker — accepting another bettor's stake on an outcome and paying out if the outcome occurs, keeping the stake if it doesn't.

Comparing odds across multiple sportsbooks before placing a bet to find the most favorable price.

The depth of a market — how much you can bet at a given price without significantly moving the line.

Wagering on a game that's already in progress, with odds that update continuously based on the current state of the contest.

A betting strategy where you bet two sides of the same market at different lines from different sportsbooks, creating a window where both bets win if the result lands between the two lines.

A bet on which team will win a game outright, with no point spread. American moneyline odds use negative numbers for favorites (-150 = risk $150 to win $100) and positive numbers for underdogs (+200 = risk $100 to win $200).

Odds calculated by removing the sportsbook's vig from the posted line, expressing the implied probability with no margin built in. Used as a reference for measuring expected value and as the fair-price benchmark in line shopping.

A US-licensed peer-to-peer betting exchange operating in 40+ states, where users bet against each other rather than against a sportsbook. No vig is built into the odds — Novig charges a small commission on winning bets instead.

A sportsbook licensed outside the United States (commonly in Curaçao, Costa Rica, or Antigua) that accepts US customers. Examples include Bovada, BetOnline, MyBookie, and Bookmaker.eu. Operates outside US state regulatory frameworks.

A list of buy and sell orders at different price levels, used by exchanges and prediction markets to match trades.

A bet on whether the combined score of both teams will be over or under a number set by the sportsbook. Independent of who wins or loses; only the total points/runs/goals matter.

A combined bet where multiple selections must all win for the bet to pay. The odds multiply across legs, producing larger potential payouts but compounded vig that heavily favors the book.

A Curaçao-licensed offshore sportsbook widely regarded as the sharpest in the world. Pinnacle accepts unlimited stakes from professional bettors, posts lines with industry-low vig of 2–3%, and uses its order flow to set the closing line that other sportsbooks copy.

A handicap that levels the playing field between two teams. The favorite must win by more than the spread; the underdog can win outright or lose by less than the spread. Half-point lines (-3.5, +6.5) prevent ties (pushes).

A blockchain-based prediction market offering binary contracts on global events, settled in USDC stablecoin. The largest prediction market by trading volume worldwide, with deep liquidity on politics, crypto, sports, and culture.

A bet where the offered odds imply a lower probability than the true probability of the outcome — meaning the expected return over many repetitions is positive. Long-term profitability in sports betting comes from consistently placing +EV bets, regardless of whether any individual bet wins or loses.

A trading platform where users buy and sell binary contracts on event outcomes. A YES contract pays $1 if the event occurs and $0 if it doesn't; the current price reflects the crowd's estimated probability. Kalshi, Polymarket, and PredictIt are the leading prediction markets.

The aggregate of bets placed by recreational bettors — high in volume but typically smaller individual sizes than sharp action.

NHL's version of a point spread, almost always set at 1.5 goals.

When the result of a bet lands exactly on the line, neither winning nor losing — stakes are returned with no profit or loss.

A bankroll management approach that stakes one-quarter of the bet size recommended by the Kelly Criterion formula. Reduces variance and drawdown risk at the cost of slower long-term growth — widely considered the practical default for serious sports bettors.

Lower-than-standard vig pricing on a market, typically -105 instead of -110, offered by sharper books and as occasional promotions.

When a betting line moves opposite to the direction of public betting volume — typically a signal of sharp action.

A wager that breaks a list of bets into multiple smaller parlays — every possible combination of a given size.

MLB's version of a point spread, almost always set at 1.5 runs.

A parlay combining multiple bets from a single game, typically with adjusted payouts to account for correlation.

A sportsbook that accepts large bets from professional bettors, adjusts lines quickly based on action, charges low vig (2–3%), and rarely limits winning customers. Pinnacle, Circa Sports, and Bookmaker.eu are leading examples.

Bets placed by professional or highly-informed bettors, characterized by large size and strong predictive power on line movement.

A sportsbook that prices markets to attract recreational action rather than match sharp consensus, charges higher vig, and limits or bans customers who show sustained edge. Most major US retail sportsbooks operate as soft books.

A binary financial contract listed on a CFTC-regulated exchange that pays $1.00 if a sports event resolves a certain way, $0.00 otherwise. Functionally similar to a sports bet but legally classified as a derivative trade rather than gambling, which allows the platform to operate under federal financial regulation rather than state gambling laws.

A sudden, sharp line movement caused by significant action from professional bettors hitting the market simultaneously.

A parlay variant that lets you adjust spreads and totals in your favor at the cost of reduced odds.

The actual likelihood of an outcome, with vig removed. Estimated by taking a sharp book's implied probabilities and dividing each by their combined total to get values that sum to 100%.

A standardized betting amount, usually 1-2% of total bankroll, used to compare and track betting performance regardless of stake size.

The natural fluctuation in betting results around the long-term expected outcome — winning or losing streaks that don't reflect the underlying skill or edge.

The margin a sportsbook charges, expressed as the difference between the combined implied probabilities of all outcomes and 100%. Standard retail vig is 4–6%; sharp books charge 2–3%; exchanges have no vig but charge commission.

When a bet is cancelled and the stake refunded due to a postponement, rule violation, or qualifying event not occurring.