Sports betting glossary
- American odds
- Odds shown as the profit on a $100 stake (+150) or the stake needed to win $100 (−150). More
- Arbitrage (arb)
- Backing every outcome at prices whose implied probabilities add to less than 100% after costs, so the payout is the same whichever side wins. More
- Ask
- The lowest price a seller will accept on an exchange. Buying now pays the ask.
- Bankroll
- The money set aside for betting, separate from money you need for anything else. More
- Bid
- The highest price a buyer will pay on an exchange. Selling now gets the bid.
- Break-even probability
- The win rate a price needs to neither win nor lose over time: 1 ÷ decimal odds, plus any fee. More
- Calibration
- How well a model’s probabilities match outcomes. A calibrated model’s 60% calls win about 60% of the time. More
- Closing line value (CLV)
- How much better your price was than the market’s last price before the start. Consistently positive CLV is the best early sign of an edge. More
- Closing line
- The last price before a game starts, after the market has absorbed the most news.
- Consensus line
- A fair price built by devigging several books and averaging them.
- Correlation
- How much two outcomes tend to happen together. Same-game parlay legs are often correlated, so multiplying their odds misprices them. More
- Decimal odds
- The total return per unit staked, including the stake. 2.50 returns $2.50 for every $1. More
- Devig
- Removing a book’s margin from its odds so the implied probabilities add to 100%. More
- Edge
- The gap between a price and your estimate of the true probability, after fees. A positive edge is a +EV bet.
- Event contract
- A contract that pays a fixed amount if an event happens, like a Polymarket or Kalshi share.
- Expected value (EV)
- A bet’s average result per unit staked over many repeats: win probability × decimal odds − 1. More
- Fractional odds
- Odds shown as profit over stake, like 3/2. Common in the UK and Ireland. More
- Hedge
- A bet on the other side of an open position to lock a profit or cut a loss, at the cost of some expected value. More
- Hold
- The share of money staked that a book expects to keep on a market if action is balanced. More
- Implied probability
- The chance a price implies: 1 ÷ decimal odds, or the price in cents on Polymarket. More
- Juice
- Another word for the vig, the margin a book builds into its prices.
- Kelly criterion
- A formula for the share of bankroll to stake on a bet with an edge so the bankroll grows fastest over time. More
- Liquidity
- How much can be bought or sold near the quoted price. Thin markets move when you trade.
- Maker
- An order that rests on the book until someone fills it. Polymarket makers pay no fee. More
- Moneyline
- A bet on who wins the game, with no point spread.
- No-vig line
- A book’s odds with the margin removed. Also called the fair line. More
- Overround
- How far a market’s implied probabilities add up above 100%. At −110/−110 it is 4.76%.
- Parlay
- One bet on several legs that all have to win. The odds multiply, and so does the margin. More
- Polymarket
- A prediction market where traders buy and sell shares that pay $1 if an outcome happens. More
- Player prop
- A bet on a player’s stat line, like points over 24.5.
- Push
- A tie against the line. The stake is returned.
- ROI (return per unit)
- Profit divided by total staked. +5% means $5 profit per $100 bet.
- A bettor or book whose prices are accurate. Sharp books take big bets and move fast on news.
- Point spread
- A handicap that the favorite must cover, like −3.5.
- Steam
- A fast, broad price move across venues, usually after sharp money or news.
- Taker
- An order that fills right away against one already on the book. Polymarket charges takers a fee. More
- Total (over/under)
- A bet on whether the combined score lands over or under a number.
- Unit
- A standard stake size, often 1% of bankroll, so records can be compared across bettors.
- Value bet
- A bet priced to pay more than its true chance is worth: a +EV bet.
- Vig (vigorish)
- The margin a book builds into its odds so the implied probabilities add to more than 100%. More
- Whale
- A trader who moves large amounts. On Polymarket every whale trade is public on-chain. More
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