A-Z dictionary of betting, casino, poker, odds, bankroll, EV, house edge, variance, and gambling math terms — each with a plain-language definition and a direct link to the matching calculator on this site.
Use the search bar to find a specific term such as house edge, vig, parlay, Kelly Criterion, or risk of ruin. You can also browse by letter using the alphabet bar. Most entries link to a calculator or tool for deeper analysis.
This glossary focuses on mathematical and strategic terms — the vocabulary you need to understand odds, edge, variance, and bankroll management — rather than general casino slang. If two terms mean nearly the same thing (e.g., Juice and Vig), the glossary cross-references them so you can move through the site faster.
Popular Gambling Terms
House Edge
Expected Value
Implied Probability
Vig
Kelly Criterion
Risk of Ruin
RTP
CLV
Arbitrage
Variance
Expected Value
Implied Probability
Vig
Kelly Criterion
Risk of Ruin
RTP
CLV
Arbitrage
Variance
A
- Accumulator (Acca)
- A single bet combining multiple selections. All legs must win for the bet to pay out. Also called a Parlay.
Parlay Calculator → - American Odds
- Odds format used in the US. +150 shows the profit on a $100 stake. -150 shows how much you have to bet to win $100.
Odds Converter → - Arbitrage (Arb)
- Placing bets on every possible outcome of an event across different bookmakers so that the combined implied probability is below 100%. The price gap between books locks in a guaranteed profit, regardless of which side wins.
Arbitrage Calculator → - Asian Handicap
- A handicap market that eliminates the draw as an outcome. Quarter lines (e.g., -0.25, +0.75) split the stake across two adjacent whole or half handicaps.
Asian Handicap Calculator →
B
- Bankroll
- The total amount of money set aside exclusively for wagering. A separate bankroll is the foundation of disciplined staking strategies like Kelly or unit-based betting.
- Basic Strategy (Blackjack)
- The mathematically optimal play for every Blackjack hand based on the dealer’s upcard. Following basic strategy reduces the house edge to roughly 0.5% on standard six-deck games.
Blackjack Strategy → - Bet Builder (SGP)
- A bet combining multiple selections from the same event (also called a Same Game Parlay). Bookmakers apply a correlation discount to the final odds, since the legs are not statistically independent.
Bet Builder Calculator → - Bonus Buy (Feature Buy)
- Paying a multiplier of the base bet (typically 50–100x) to skip directly to a slot’s bonus round. Bonus buys have higher variance and a slightly different RTP than the base game.
Bonus Buy Calculator → - Both Teams to Score (BTTS)
- A football market on whether both teams score at least one goal in regulation time.
BTTS Calculator →
C
- Cash Out
- Settling a bet early at a price set by the bookmaker. Cash out prices are usually worse than the equivalent manual hedge on an exchange because they include an additional margin.
Cash Out vs Hedging → - Closing Line Value (CLV)
- The difference between the odds you took and the odds the market settled at when the event started. Sustained positive CLV is the strongest available indicator of long-term betting skill.
CLV Calculator → - Confidence Interval
- A statistical range where the true value of a metric (such as your true ROI) is likely to fall, given the data sample you have. Wider intervals mean more uncertainty.
Portfolio Tracker → - Correct Score
- A bet on the exact final score of a match. High odds, low probability, and usually a high bookmaker margin.
Correct Score Calculator → - Correlation
- The statistical relationship between selections in the same event. If a star striker scoring is correlated with the match going Over 2.5 goals, combining the two as a parlay should pay less than the product of their independent odds.
D
- Decimal Odds
- Total return per $1 staked, including the stake. Odds of 2.50 mean a $1 bet returns $2.50 ($1.50 profit).
Odds Converter → - Devig (De-juice)
- Removing the bookmaker margin from a set of odds to estimate the fair (no-vig) probability of each outcome.
No-Vig Calculator → - Dixon-Coles Model
- A correction to the Poisson model for football match outcomes. It adjusts the probabilities of low-scoring results (0-0, 1-0, 0-1, 1-1) where pure Poisson tends to misprice the data.
xG Calculator → - Double Chance
- A bet covering two of three match outcomes (1X = home or draw, X2 = draw or away, 12 = either team wins). Lower odds in exchange for higher coverage.
Double Chance Calculator → - Draw No Bet (DNB)
- A bet where the stake is returned if the match ends in a draw. Mathematically equivalent to Asian Handicap 0.
DNB Calculator → - Dutching
- Splitting your stake across multiple selections so that whichever one wins, your profit is the same. Used to back several contenders in the same market.
Dutching Calculator →
E
- Each-Way (E/W)
- Two equal bets in one: half on the selection to win outright, half on it to place within a defined finishing range. Common in horse racing and golf outrights.
Each-Way Calculator → - Edge
- A bettor’s mathematical advantage over the offered odds. Edge = (True Probability × Decimal Odds) − 1. A positive edge means a bet is profitable in the long run; a negative edge means it loses money over time.
- Expected Goals (xG)
- A statistical measure of the quality of scoring chances in football. Each shot is assigned a probability of becoming a goal based on shot location, angle, body part, and other factors. xG is more stable than actual goals over short samples.
xG Calculator → - Expected Value (EV)
- The average profit or loss of a bet over the long run. In betting, EV compares your estimated true probability with the odds being offered. Positive EV means the price is better than the probability suggests; negative EV means the bet is mathematically losing.
EV Calculator →
F
- Fair Odds
- Odds with the bookmaker margin removed, reflecting the true probability of an outcome. Also called No-Vig odds.
Fair Odds Calculator → - Flat Betting
- Wagering the same amount on every bet regardless of perceived edge or confidence. The simplest staking method, used as a baseline before adopting more advanced approaches like Kelly.
- Fractional Odds
- Profit relative to stake, expressed as a fraction. 5/1 means $5 profit per $1 staked. The traditional UK format.
Odds Converter → - Futures (Outrights)
- Long-term bets on season or tournament outcomes (championship winner, top scorer, group winner). Capital is tied up until settlement.
Futures Hedge Calculator →
G
- Gambler’s Fallacy
- The false belief that past random results influence future independent outcomes — for example, expecting black to be “due” after a streak of red on roulette. Each spin is independent of the last.
- Gambler’s Ruin
- A theorem stating that a finite bankroll played against a negative expectation game eventually goes broke with probability 1, given enough time. The classic gambler’s ruin formula gives the probability of reaching a target before going broke for a given win probability.
Gambler’s Ruin Calculator →
H
- Half-Time/Full-Time (HT/FT)
- A bet on the result at both half-time and full-time (e.g., Home/Home, Draw/Away). Nine possible outcomes, all priced separately.
HT/FT Calculator → - Handicap
- A virtual point or goal advantage applied to one side of a market to level a mismatched contest. Comes in European (3-way) and Asian (no-draw) variants.
- Hedge
- A second bet placed on the opposing outcome of an existing position. Used to reduce risk, lock in profit, or guarantee a minimum return on a futures bet.
Hedging Calculator → - House Edge
- The casino’s long-run mathematical advantage, expressed as a percentage of each wager. A game with a 2.7% house edge is expected to keep $2.70 per $100 wagered over a large sample. House edge does not predict the result of a single session.
House Edge Comparison → - Hypergeometric Distribution
- The probability distribution for drawing successes from a population without replacement. Used in Keno, lotteries, and any game where balls or cards are drawn and not returned.
Keno Analyzer →
I
- Implied Probability
- The win probability suggested by betting odds. Decimal odds of 2.00 imply 50%; American odds of +150 imply 40%. Bookmaker odds usually include margin, so implied probability is not the same as fair probability.
Implied Probability Calculator → - In-Play (Live Betting)
- Betting while an event is in progress, with odds updating as the action unfolds.
J
- Juice (Vig, Vigorish)
- The bookmaker fee built into the odds. On a fair coin flip priced at -110/-110, the juice is the gap between true 50/50 odds and the offered price.
Margin Calculator →
K
- Kelly Criterion
- A formula for optimal bet size given your edge and the odds: f* = Edge / (Decimal Odds − 1). Kelly maximizes long-run bankroll growth in theory but is highly sensitive to edge estimation errors. Many bettors use fractional Kelly (e.g., half-Kelly) to reduce variance.
Kelly Calculator →
L
- Lay Bet
- Betting against an outcome on an exchange — taking the bookmaker’s role. The lay bettor wins if the selection does not occur and loses (the liability) if it does.
Lay Calculator → - Line
- The odds, point spread, or total currently offered by a bookmaker on an event.
M
- Margin (Overround)
- The total implied probability of all outcomes in a market minus 100%. A market summing to 105% has a 5% margin built in.
Margin Calculator → - Martingale
- A staking system that doubles the bet after every loss. It does not beat the house edge — it concentrates risk into rare catastrophic losses, constrained by bankroll size and table limits.
Martingale Simulator → - Matched Betting
- A technique that uses bookmaker free bets and bonuses combined with a lay bet on an exchange to extract guaranteed profit, regardless of the outcome.
Matched Betting Calculator → - Monte Carlo Simulation
- Running thousands or millions of randomized scenarios to estimate the probability of an outcome that is hard to compute analytically. Used for risk of ruin, bonus buy modelling, and parlay distribution.
Bonus Buy Simulator →
N
- No-Vig
- Odds with the bookmaker margin removed, leaving an estimate of fair probability. Same idea as Devig and Fair Odds.
No-Vig Calculator →
O
- Over/Under (Totals)
- A bet on whether the total (goals, points, runs) will exceed or fall below a benchmark line set by the bookmaker.
Over/Under Calculator →
P
- Parlay
- Multiple selections combined into one bet. All legs must win for the parlay to pay out. Same concept as an Accumulator.
Parlay Calculator → - Poisson Distribution
- A discrete probability distribution for the number of events in a fixed interval. Used in football models to estimate the probability of each scoreline given an expected goals figure for each team.
Poisson Calculator → - Prop Bet
- A bet on a specific occurrence within an event that does not directly determine the final result — for example, a player’s shot count, total cards, or first-quarter score.
- Provably Fair
- A cryptographic system used in crypto casinos that lets a player verify that an outcome was determined before the bet was placed and not manipulated afterwards.
- Push
- A bet that ties the line, resulting in the stake being returned. Common on whole-number handicaps and totals.
- P-Value
- The probability that a result occurred by chance under the null hypothesis. A p-value below 0.05 is the conventional threshold for statistical significance.
Portfolio Tracker →
Q
- Qualifying Bet
- A real-money bet required to unlock a bookmaker promotion, free bet, or sign-up bonus. Used as a trigger condition in matched betting workflows.
R
- Return to Player (RTP)
- The percentage of total wagered money a casino game returns to players over the long run. A 96% RTP slot has a 4% house edge.
- Risk of Ruin (RoR)
- The probability that a bankroll falls to zero, or below the minimum playable unit, before reaching a target profit. It depends on bankroll size, bet size, edge, variance, and stopping rules.
Risk of Ruin Calculator → - ROI (Yield)
- Return on Investment. ROI = Total Profit / Total Staked, usually expressed as a percentage. Yield is the same metric under a different name and is the standard measure of betting performance.
- Rule 4
- A horse racing payout deduction applied when a runner is withdrawn from a race after odds have already been taken. The size of the deduction depends on the withdrawn runner’s odds.
Horse Payout Calculator →
S
- Sharp (Sharp Bettor)
- A professional or skilled bettor whose action is respected by bookmakers. Sharp money tends to move lines.
- Spread (Point Spread)
- A handicap expressed in points. The favorite must win by more than the spread to cover; the underdog can lose by less than the spread or win outright.
Spread Calculator → - Stake
- The amount of money risked on a single bet.
- Standard Deviation
- A measure of how far results vary from the mean. In betting, higher standard deviation means more session-to-session swings around the long-run expected value.
Variance Calculator →
T
- True Odds
- The real probability of an outcome, with no bookmaker margin applied. Same concept as Fair Odds and No-Vig.
U
- Unit
- A standardized bet size, typically defined as 1% of total bankroll. Tracking results in units rather than dollars normalizes performance across different bankroll sizes.
Unit Calculator →
V
- Value Bet
- A bet where your estimated true probability is higher than the implied probability of the offered odds. Value bets have positive expected value over the long run.
Value Bet Calculator → - Variance
- A measure of how widely results fluctuate around the expected value. High-variance markets like Straight Up roulette or correct score football have wide outcome distributions; low-variance markets like even-money roulette or Banker baccarat have tighter ones.
Variance Calculator → - Vig (Vigorish)
- See Juice. The bookmaker margin built into betting odds.
W
- Wagering Requirement
- The number of times a bonus amount must be wagered before any associated winnings can be withdrawn. A common gating mechanism for casino sign-up offers.
Wagering Calculator → - Win Rate
- The percentage of bets resolved as wins. Win rate alone does not measure profitability — at -110 odds, you need to win above 52.4% just to break even. Use ROI, not win rate, to evaluate edge.
X
- xG (Expected Goals)
- A statistical measure of football scoring chance quality. See the full Expected Goals (xG) entry above for details.
xG Calculator →
Z
- Zero
- The green pocket on a roulette wheel that gives the casino its house edge on even-money bets. European roulette has one zero (2.70% edge); American roulette adds a double zero (5.26% edge).
Roulette Risk of Ruin →
This glossary focuses on mathematical and strategic gambling terms. For specific calculations, use the linked tools. Missing a term? Let us know.