Vig
The sportsbook's built-in margin. Both sides of a bet add up to more than 100%. We strip the vig to see the true market probability.
Vig (also called juice) is the sportsbook's built-in margin. On a two-way market the two implied probabilities add up to more than 100%. That extra is not anyone's true chance of winning — it is the book's cut.
A standard -110 / -110 market totals about 104.8%. The extra 4.8% is vig. A juicier market (-115 / -115, or worse) hides more margin and makes the raw implied probabilities look more certain than they are.
We strip the vig so the two sides sum to 100% and you can compare books without the margin baked in. Edge and win probability on Odds on Deck are both computed after that step.
Example
-110 on both sides = ~104.8% total. The extra 4.8% is the book's cut.