Arbitrage Betting Glossary
Updated October 16, 2026
Plain definitions for the terms used across the guides. Each one links to the guide that covers it in more depth.
Arbitrage (arb)
Backing every outcome of an event at different books when their prices add up to less than 100% implied probability. With the right stakes, every outcome returns the same amount. More in What Is Arbitrage Betting?
Implied probability
The chance of an outcome that a price assumes. For decimal odds it’s 1 divided by the odds, so 2.00 implies 50% and 1.91 (-110) implies 52.38%. More in the arbitrage math guide.
Vig
The margin a sportsbook builds into its prices, also called juice. It’s the reason both sides of a -110/-110 line add up to more than 100%. More in the prediction markets guide.
Overround
How far a market’s implied probabilities add up past 100%. Two sides at -110 imply 52.38% each, 104.76% together, so the overround is 4.76%. An arb needs the best prices across books to come in under 100%. More in the arbitrage math guide.
Hold
The book’s built-in margin, quoted the way this site and most odds tools quote it: the overround on a market. A -110/-110 line has a 4.76% hold. Measured as a share of the money wagered with balanced action on both sides, the same line keeps about 4.55%.
No-vig price
A price with no margin in it, where both sides add up to exactly 100%. Prediction markets price close to this when they charge little or no fee, as Novig does on pre-game straight trades. More in the prediction markets guide.
Leg
One of the bets inside an arb, a hedge or a parlay. A two-way arb has two legs, one on each outcome. More in the stake sizing guide.
Stake sizing
Splitting a total stake across the legs so every outcome returns the same amount. Each leg’s share equals its implied probability divided by the total. More in the stake sizing guide.
Hedge
A bet on the other side of a bet you already hold, sized to lock in a profit or get your stake back. More in How to Hedge a Bet.
Middle
Two bets on opposite sides of a spread or total at different lines, such as Over 44.5 and Under 47.5. A final result between the two lines wins both bets. The hedge and middle calculator shows the payout in each case.