Glossary
18 terms, defined plainly.
RTP (Return to Player)
The long-run percentage of total stakes a game returns to players. A 96% RTP means an average theoretical cost…
House Edge
The casino’s built-in mathematical advantage, equal to 100% minus RTP. It guarantees profit over volume, not e…
Vig / Overround
The bookmaker’s margin baked into odds, making implied probabilities sum to more than 100%.…
Implied Probability
The break-even win chance the odds represent: 100 ÷ decimal odds.…
Expected Value (EV)
The average result of a bet if repeated infinitely: probability-weighted profit minus loss.…
Variance
How far real results swing from the expected value; high-variance games have rarer, larger outcomes.…
Volatility
A slot’s payout shape: low pays small and often, high pays big and rarely.…
Kelly Criterion
A formula for the bankroll fraction that maximises long-run growth given your edge.…
Closing Line Value
The difference between the odds you took and the market’s closing odds — the best skill signal in betting.…
Arbitrage
Backing all outcomes across bookmakers so any result yields a guaranteed profit.…
Dutching
Staking several selections so each returns the same profit whichever wins.…
Matched Betting
Using back and lay bets to extract bookmaker bonuses with little or no risk.…
Lay Bet
A bet that a selection will NOT happen, placed on a betting exchange.…
Liability
The amount risked on a lay bet if the selection wins.…
Wagering Requirement
How many times a bonus must be staked before withdrawal (e.g. ×35).…
Risk of Ruin
The probability of losing your whole bankroll before variance turns positive.…
Edge
Your advantage over the odds: estimated probability minus implied probability.…
Parlay / Accumulator
A single bet combining multiple selections where all must win.…
