House Edge

The built-in mathematical advantage the casino has on a game. It is why, over time, the expected result of gambling is a loss. It ranges from ~0.5% (blackjack) to 5%+ (some slots, American roulette).

In practice. European roulette’s 2.7% edge means that, over the long run, the casino keeps about $2.70 of every $100 staked.