# Glossary > Independent. Not affiliated with, endorsed by or sponsored by Novig. Canonical: https://novigapi.com/learn Plain definitions of vig, devig, CLV, EV, Kelly, order books and Novig's exchange terms, each with a worked example. - [Vig](https://novigapi.com/learn/vig): The vig is the margin a sportsbook builds into its odds, so that the implied probabilities of all outcomes add up to more than 100%. - [Devig](https://novigapi.com/learn/devig): To devig is to strip the bookmaker margin out of a set of odds so the implied probabilities sum to exactly 100%, leaving an estimate of the fair price. - [No-vig odds](https://novigapi.com/learn/no-vig-odds): No-vig odds are the prices a market would show with the bookmaker margin removed, so the implied probabilities of all outcomes add to exactly 100%. - [Fair odds](https://novigapi.com/learn/fair-odds): Fair odds are the odds that exactly reflect an outcome's estimated true probability, with no margin for the house, so a bet at fair odds has zero expected value. - [Implied probability](https://novigapi.com/learn/implied-probability): Implied probability is the chance of an outcome that a set of odds suggests, and it is also the win rate you need to break even at that price. - [Overround](https://novigapi.com/learn/overround): The overround is the amount by which the implied probabilities of every outcome in a market add up to more than 100%. - [Hold](https://novigapi.com/learn/hold): Hold is the percentage of the money wagered on a market that the bookmaker expects to keep if it takes balanced action on every outcome. - [Closing line value](https://novigapi.com/learn/closing-line-value): Closing line value is how much better the price you took was than the final fair price just before the event started. - [Positive EV](https://novigapi.com/learn/positive-ev): A positive EV bet is one whose price pays more than its fair odds, so it is expected to make money on average over many repetitions. - [Expected value](https://novigapi.com/learn/expected-value): Expected value is the average amount a bet wins or loses per play if it could be repeated many times at the same price and probability. - [Kelly criterion](https://novigapi.com/learn/kelly-criterion): The Kelly criterion is a formula for the fraction of your bankroll to stake on a positive EV bet so that long-run bankroll growth is as fast as possible. - [Arbitrage](https://novigapi.com/learn/arbitrage): Arbitrage is betting every outcome of a market across different books or exchanges at prices that guarantee a profit whatever happens. - [Middle](https://novigapi.com/learn/middle): A middle is a pair of opposite bets on different lines of the same market that both win if the result lands between the two numbers. - [Steam move](https://novigapi.com/learn/steam-move): A steam move is a sudden, sharp line movement in the same direction across many books at once, usually caused by coordinated or respected money. - [Reverse line movement](https://novigapi.com/learn/reverse-line-movement): Reverse line movement is when a line moves against the side most bettors are backing, which suggests the larger or sharper money is on the other side. - [Sharp money](https://novigapi.com/learn/sharp-money): Sharp money is money wagered by bettors with a demonstrated long-run edge, whose bets move lines because books and markets respect their information. - [Maker and taker](https://novigapi.com/learn/maker-taker): A maker posts a resting order that waits on the book, and a taker submits an order that matches a resting order immediately. - [Order book](https://novigapi.com/learn/order-book): An order book is the list of resting buy orders on an exchange market, organized by price, showing how many contracts traders will trade at each level. - [Bid-ask spread](https://novigapi.com/learn/bid-ask-spread): The bid-ask spread is the gap between the highest price a buyer will pay and the lowest price a seller will accept on the same outcome. - [Open interest](https://novigapi.com/learn/open-interest): Open interest is the number of contracts in a market that have been bought and not yet closed out or settled. - [Liquidity](https://novigapi.com/learn/liquidity): Liquidity is how much you can trade in a market, and how quickly, without moving the price against yourself. - [Event contract](https://novigapi.com/learn/event-contract): An event contract is a financial contract that pays a fixed amount if a specified event happens and nothing if it does not. - [Prediction market](https://novigapi.com/learn/prediction-market): A prediction market is an exchange where people trade contracts on future events, and contract prices act as crowd estimates of each event's probability. - [Betting exchange](https://novigapi.com/learn/betting-exchange): A betting exchange is a marketplace where bettors trade against each other at prices they set, while the exchange takes a fee instead of acting as the bookmaker. - [Participation protection](https://novigapi.com/learn/participation-protection): Participation protection is a Novig rule for certain NFL and NBA player props that resolves the market at its pregame fair price if the player does not play after halftime. - [RFQ parlay](https://novigapi.com/learn/rfq-parlay): An RFQ parlay is a parlay priced by request for quote: the exchange asks market makers to quote a price for the exact combination, and the best quote wins. - [American odds](https://novigapi.com/learn/american-odds): American odds express a price as the amount you win on a $100 stake (positive numbers) or the amount you must stake to win $100 (negative numbers). - [Decimal odds](https://novigapi.com/learn/decimal-odds): Decimal odds express a price as the total amount returned per unit staked, including the stake, so 2.50 returns $2.50 for every $1 bet. - [Line movement](https://novigapi.com/learn/line-movement): Line movement is any change in a market's price or point line between when it opens and when it closes. - [Hedging](https://novigapi.com/learn/hedging): Hedging is placing a bet on the opposite outcome of a position you already hold, to reduce risk or lock in a guaranteed result. - [Bonus bet](https://novigapi.com/learn/bonus-bet): A bonus bet is promotional credit from a sportsbook that you can wager but whose stake is not returned if the bet wins, so only the profit pays out. - [Round robin](https://novigapi.com/learn/round-robin): A round robin is a set of smaller parlays built from every combination of a chosen group of picks, so you can still profit if not every pick wins. - [Market maker](https://novigapi.com/learn/market-maker): A market maker is a trader or firm that posts resting orders on both sides of a market, earning the spread in exchange for providing liquidity. - [Limit order](https://novigapi.com/learn/limit-order): A limit order is an order to buy at a set price or better, which rests on the order book until another trader fills it or you cancel it. --- Get a free API key: https://novigapi.com/sign-up . 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