Glossary

House Edge

The casino's built-in mathematical advantage expressed as a percentage of each bet. A 1% house edge means the casino keeps an average of $1 for every $100 wagered. Over millions of bets this is extremely reliable — it's how casinos stay profitable regardless of short-term swings.

Rakeback

A refund of a portion of the house edge back to the player, usually expressed as a percentage. A 50% rakeback on a 2% house edge game means you effectively pay only 1%. This is the single biggest lever a player has for reducing long-run cost.

RTP (Return to Player)

The percentage of total wagered money a game returns to players over time. The inverse of house edge: a 99% RTP means a 1% house edge. A 100% RTP would be a perfectly fair game with no edge either way.

EV (Expected Value)

The average outcome of a bet if you played it infinitely many times. A bet with positive EV returns more than it costs on average; negative EV loses money on average. Most casino bets have negative EV — the edge is what makes the casino profitable.

Variance

The statistical measure of how much results deviate from the expected value in the short run. High-variance games produce wild swings. Low-variance games stay closer to EV over fewer rounds.

Volatility

Often used interchangeably with variance in a casino context. A high-volatility game has infrequent but large wins; a low-volatility game has frequent small wins. Same expected value, very different experience.

Standard Deviation

A measure of how spread out outcomes are around the average. High standard deviation means big swings — you can be way up or way down in the short run even when your EV is negative. It's the mathematical description of variance.

Bankroll

The total amount of money you have set aside for gambling. Managing your bankroll — how much you bet per round relative to your total — is one of the most important decisions a gambler makes.

Bet Size

The amount wagered on a single round or hand. Larger bets mean larger absolute swings — the same house edge costs more in dollar terms the bigger you bet.

Wager

The amount bet on a single outcome. Synonymous with bet size. Many bonus and rakeback structures are calculated based on total wager volume — how much you've bet in total, regardless of outcomes.

Payout

How much you receive back on a winning bet. Expressed as a ratio (3:2 pays $15 on a $10 bet), a multiplier (2× returns double your bet), or a total return including the original stake.

Multiplier

The factor by which your bet is multiplied when you win. A 2× multiplier on a $10 bet returns $20 (profit of $10). Higher multipliers mean lower hit rates — the payouts are balanced against how rarely they occur.

Simulation

Running thousands or millions of virtual game rounds using real probability distributions to estimate outcomes. Simulations reveal what will happen over long time horizons — things like expected loss, volatility, and the probability of going broke.

Unit

A standardized bet size used to track results relative to your bankroll, not in dollar terms. Measuring wins and losses in units keeps performance comparable across different stake levels.

Paytable

The table listing all possible winning hands or outcomes and their respective payouts. In video poker, different paytables with different payouts for the same game can shift the house edge by several percent.

Leaderboard

A casino promotion where players earn points based on wager volume or generated value and compete for prize pools. They can further reduce the house edge

Auto Cashout

In crash games, a pre-set multiplier at which your bet is automatically cashed out. If the game crashes before reaching it, you lose. If it passes, you win at that multiplier. Useful so you don't have to react in real time.

Martingale

A betting system where you double your bet after every loss, trying to recover all losses with one win. It feels safe but is mathematically flawed — a long losing streak (which will happen eventually) wipes out the entire bankroll or hits table limits.

Paroli (Anti-Martingale)

A betting system where you double your bet after every win instead of every loss. The idea is to ride winning streaks and limit losses to your base bet. It's less dangerous than the Martingale but still doesn't change the underlying EV — no betting system can overcome a negative house edge.

Implied Probability

The probability of an outcome implied by the odds being offered. For example, odds of 2.00 (even money) imply a 50% chance. If the true probability is higher than the implied one, you have a positive EV bet.

Parlay

A single bet that chains multiple outcomes together — all must win for you to collect. The payout multiplies with each leg, but so does the risk.

Vigorish (Vig)

The cut a sportsbook takes on every bet, built into the odds. If both sides of a bet are priced at -110, the vig is roughly 4.5%. Also called juice. Reducing the vig you pay by shopping for better lines is one of the few edges available in sports betting.

Basic Strategy

The mathematically optimal set of decisions (hit, stand, double, split, surrender) based only on your hand total and the dealer's upcard. Playing perfect basic strategy gives you the lowest possible house edge.

Dealer Upcard

The one card the dealer shows face-up at the start of a blackjack hand. The upcard heavily influences your strategy — a dealer showing a 6 is in a much weaker position than one showing an Ace.

Double Down

A blackjack move where you double your original bet in exchange for receiving exactly one more card. It's most powerful when you have a strong total (like 10 or 11) and the dealer is showing a weak card.

DS (Total Wager) House Edge

A house edge calculation that accounts for the total amount wagered — including all doubles and splits — not just the original bet. This gives a more accurate picture of cost per dollar actually put at risk. BetTheory labels these DS Optimal and DS Basic.

Hard Hand

A blackjack hand with no Ace, or with an Ace that can only count as 1 without busting (e.g., Ace + 8 + 7 = 16, Ace must be 1). Contrasted with a soft hand.

Soft Hand

A blackjack hand containing an Ace counted as 11 without busting (e.g., Ace + 6 = soft 17). You can't bust with one more card on a soft hand, which makes it play differently to a hard hand with the same total.

Infinite Deck

A mathematical model where cards are drawn with replacement — as if from an infinitely large shoe. This makes the math exact and eliminates the card-removal effects you get in real finite-deck games. Duel's internal blackjack uses this model.

Insurance

A side bet offered when the dealer shows an Ace. It pays 2:1 if the dealer has a natural blackjack. Insurance has a negative EV for the player in almost all cases and is generally not recommended.

Natural Blackjack

An Ace and a 10-value card dealt as the first two cards — the best possible hand. It typically pays 3:2 (or sometimes 6:5, which is worse for the player). A natural beats a dealer hand of 21 that required more than two cards.

Optimal Play

In video poker and blackjack, the strategy that maximizes EV by considering all available information, including the exact card composition of your hand (not just the total). Optimal play is slightly better than basic strategy in finite-deck games.

Split

A blackjack option when your first two cards are a pair — you separate them into two independent hands, each with a separate bet. Splitting Aces and 8s is almost always correct; splitting 10s almost never is.

Shoe

A device holding multiple decks of cards (typically 4, 6, or 8) used in blackjack. More decks slightly increase the house edge.

Surrender

A blackjack option to fold your hand and recover half your bet. Late surrender (the common version) is available after the dealer checks for blackjack. It's correct on hands like hard 16 vs. dealer 9, 10, or Ace.

Push

A tie — you and the dealer finish with the same total. Your original bet is returned with no profit or loss.