Casino & Odds Glossary — LearnTheOdds

Core odds math

House edge: The casino’s built-in advantage on a bet, as a percent of the amount wagered — the long-run share the house keeps. A 1% edge means you lose, on average, $1 per $100 wagered (not per visit). See The House Edge and the house edge by game.
RTP (Return to Player): The flip side of the house edge: the long-run share of wagers paid back. 96% RTP = a 4% house edge. A high RTP is still a losing game over time — it just loses slower. See RTP explained.
Expected value (EV): The average result of a bet if you made it many times — each outcome weighted by its probability. Casino bets have negative EV by design. See Expected Value explained.
Variance: How much actual results swing around the average. High variance = bigger, rarer wins and longer dry spells; it’s why you can win in the short run at a game you’re mathematically destined to lose. See Variance.
Volatility: Practically a synonym for variance, used most often for slots. Two machines can share the same RTP yet feel completely different — one drips small wins, the other pays rarely but big. See the volatility guide.
Hit frequency: How often a bet (especially a slot spin) returns anything at all. A 20% hit frequency means roughly one in five spins pays — independent of how generous those payouts are.
Risk of ruin: The probability of losing your whole bankroll before you stop. It rises with bet size, the house edge, and how long you play. See bankroll management.
Vig / juice / commission: Different names for the cut the house takes on certain bets — e.g. the 5% commission on a winning Baccarat Banker bet — which is how the edge is collected on an otherwise near-even wager.
True odds vs payout odds: True odds = the real probability of an outcome. Payout odds = what the casino actually pays. The gap between them is the house edge — e.g. a single-number roulette win is a true 37-to-1 but pays only 35-to-1.

Bankroll & play

Bankroll: The money you’ve set aside to gamble with — ideally an amount you can fully afford to lose. Sizing bets as a small fraction of it is what keeps a normal losing streak from wiping you out.
Unit: One standard bet size, used to talk about results independent of dollars (“up 12 units”). Sizing a unit at ~1–2% of bankroll is a common discipline.
Comp: A complimentary perk — free play, food, rooms — a casino gives based on your tracked play (your theoretical loss). Comps are a rebate on expected losses, not free money, and are generally taxable.
Theoretical loss (theo): The casino’s expected profit from your play = total wagered × house edge. It drives your comp tier, and it’s also the basis for most affiliate commissions.

Table-game terms

Even-money bet: A bet that pays 1:1 (win $10 on a $10 stake). Roulette red/black and the Pass Line are close to — but never exactly — a 50/50 proposition, which is precisely where the edge hides.
Push: A tie between you and the house — no win, no loss, your stake is returned.
Natural / Blackjack: An ace plus a ten-value card on the first two cards (21). It typically pays 3:2 — the 6:5 tables quietly raise the house edge, which is why we flag them. See how to play blackjack.
Insurance: A blackjack side bet offered when the dealer shows an ace. It’s a sucker bet for the basic-strategy player — a separate wager with its own steep edge.
Surrender: A blackjack option to fold a bad hand and reclaim half your bet. When available, it slightly lowers the house edge — one of the few player-favorable rules.
Pass / Don’t Pass: The two core craps line bets (1.41% / 1.36% edge). Backing them with Free Odds is the cheapest action in the casino. See how to play craps.
Come-out roll & Point: The come-out is the first roll of a craps round; if it sets a Point (4,5,6,8,9,10), the shooter must repeat it before a 7 to win the Pass Line.
Free Odds: A craps bet, available only behind a line bet, that pays true odds — a 0% house edge. The only break-even bet on the floor; everything else carries an edge.
Banker / Player / Tie: The three main baccarat bets. Banker (1.06% edge after commission) is mathematically best; the Tie (~14%) is a trap. See how to play baccarat.
Inside / Outside bets: Roulette bet groups — inside (single numbers and small clusters, high payout/low chance) vs outside (red/black, odds/evens, dozens). On a given wheel they all carry the same edge. See how to play roulette.

Slots

RNG (Random Number Generator): The algorithm that decides every spin’s outcome the instant you press spin — independent of the last spin and of how long since a jackpot. See how RNG works.
Paytable: The map from outcomes to payouts. Real slots keep it hidden; our transparent slots model shows every paytable openly so you can see exactly where the RTP comes from.
Payline: A line across the reels that pays when matching symbols land on it. More paylines mean more frequent small wins — but you’re usually betting on all of them, so it doesn’t change the underlying edge.
Reel & symbol: The spinning columns and the icons on them. In our model the reels are a presentation of an already-decided number — the symbols communicate the win tier, the number is the exact result.
Progressive jackpot: A top prize that grows as players feed the machine until someone hits it. The jackpot contribution is baked into the (lower) base-game RTP. See progressive jackpots.
Max win multiplier: The largest payout a slot can return, expressed as a multiple of your stake (e.g. 5,000×). High max-win machines are almost always high-volatility — long droughts buy the rare big hit.

Online & sweepstakes

Sweepstakes (social) casino: A site that offers casino-style games under a sweepstakes legal model rather than real-money gambling, using a dual-currency system. Availability and legality vary by state. See our review.
Gold Coins vs Sweeps Coins: The two currencies on most sweeps sites: Gold Coins are for-fun only (no cash value); Sweeps Coins can be redeemed for prizes. The distinction is what keeps the model on the sweepstakes side of the law.
Provably fair: A cryptographic scheme that lets you verify a result wasn’t altered after your bet — it proves fairness of the draw, not that the game is beatable (the house edge is unchanged). See what provably fair means.

Systems & fallacies

Martingale: A doubling-after-each-loss system that feels foolproof and isn’t — table limits and a finite bankroll guarantee an eventual catastrophic loss, and the per-bet edge never changes. See is the Martingale profitable?
Gambler’s fallacy: The false belief that an outcome is “due” after a streak (red is due, the machine is cold). Independent events have no memory. See the gambler’s fallacy.
Card counting: Tracking the ratio of high to low cards remaining in blackjack to bet bigger when the deck favors the player. Legal, genuinely shifts the edge, hard to do, and casinos actively counter it — it is not a fit for most games or online RNG play.
Near-miss: When a slot stops just short of a jackpot to make a loss feel close. On real machines this is an engineered presentation trick, not a real “almost” — our model never fakes one. A loss is a loss.

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