The house edge is the built-in mathematical advantage a casino holds on a game, expressed as the share of each bet it expects to keep on average over the long run.
It is the reason casinos are profitable, and the reason the expected result of sustained wagering is a loss rather than a win. The edge is baked into the rules and payouts of every game, and no betting system removes it. A short session can still end ahead through chance, but the more you play, the closer your results tend to drift toward that built-in edge.
A clear example is European roulette. The wheel has 37 pockets, numbered 0 to 36. A bet on a single number pays 35 to 1, yet there are 37 possible outcomes, so a genuinely fair payout would be 36 to 1. That one-unit gap, spread across 37 outcomes, is the house edge, and it is why the casino comes out ahead over time even though any single spin is unpredictable.
The house edge is the mirror image of return to player, or RTP: a game keeping 3% as its edge returns roughly 97% to players over the long run.
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