---
title: "A to Z of terms"
url: https://gagamblinghelpline.org/terms/
description: "An alphabetical index of fifty terms from the mathematics of games of chance, each with a one-line gloss and its topic chapter."
---

# A to Z of terms

Fifty entries, grouped by first letter. Twenty-four of the twenty-six letters carry at least one entry. Each entry gives a one-line plain-language gloss and its topic chapter; entries carrying a figure also name the base that figure is measured against.

## A

[Ante](https://gagamblinghelpline.org/terms/#A)

A fixed amount every player puts up before a hand is dealt, forming the pot the hand is played for.

GAMES AND RULES

[Advantage](https://gagamblinghelpline.org/terms/#A)

The share of each amount staked that one side of a game expects to keep once every outcome is weighted by its probability.

per unit staked

HOUSE ADVANTAGE

## B

[Bankroll](https://gagamblinghelpline.org/terms/#B)

The total amount set aside for play, against which the spread of results over many trials is measured.

VARIANCE AND STREAKS

[Binomial distribution](https://gagamblinghelpline.org/terms/#B)

The distribution of the count of successes in a fixed number of independent trials that each succeed with the same probability.

VARIANCE AND STREAKS

[Bookmaker's margin](https://gagamblinghelpline.org/terms/#B)

The amount by which the prices offered on every outcome of a market sum to more than one whole probability.

per unit staked

ODDS AND PRICES

## C

[Combination](https://gagamblinghelpline.org/terms/#C)

A selection in which order does not matter; the count of six-from-forty-nine selections is 13,983,816.

LOTTERIES AND DRAWS

[Come-out roll](https://gagamblinghelpline.org/terms/#C)

The first roll of a dice sequence, which either settles the bet at once or fixes the number the sequence must then repeat.

GAMES AND RULES

[Cumulative probability](https://gagamblinghelpline.org/terms/#C)

The probability that a result falls at or below a stated value, found by adding the probabilities of every outcome up to it.

PROBABILITY

## D

[Decimal odds](https://gagamblinghelpline.org/terms/#D)

A price stated as the total return per one unit staked, so that its reciprocal is the implied probability.

per unit staked

ODDS AND PRICES

[Dependent events](https://gagamblinghelpline.org/terms/#D)

Events where the outcome of one changes the probability of another, as when cards are dealt without replacement.

PROBABILITY

## E

[Even-money bet](https://gagamblinghelpline.org/terms/#E)

A bet returning one unit of profit per unit staked, quoted as 1/1, 2.00 or +100.

ODDS AND PRICES

[Expected value](https://gagamblinghelpline.org/terms/expected-value/)

The probability-weighted average of every outcome of a bet; on a 37-pocket wheel it is minus one part in thirty-seven.

per unit staked

PROBABILITY

## F

[Fair game](https://gagamblinghelpline.org/terms/#F)

A game whose expected value is zero, meaning the prize paid matches exactly the true odds against the result.

PROBABILITY

[Fractional odds](https://gagamblinghelpline.org/terms/#F)

A price stated as profit against stake, so 5/1 returns five units of profit for one unit risked.

ODDS AND PRICES

## G

[Gambler's fallacy](https://gagamblinghelpline.org/terms/#G)

The belief that a run of one outcome makes the opposite outcome more likely on the next independent trial.

PROBABILITY

[Gambler's ruin](https://gagamblinghelpline.org/terms/#G)

The result that a player with finite funds facing a negative expectation and unlimited trials is eventually certain to reach zero.

VARIANCE AND STREAKS

## H

[Hit frequency](https://gagamblinghelpline.org/terms/#H)

The proportion of trials returning anything at all, set independently of how much is returned in total.

per spin

GAMES AND RULES

[Hold](https://gagamblinghelpline.org/terms/#H)

The proportion of the amount staked that a game or table retains once play has finished.

per unit staked

HOUSE ADVANTAGE

[House edge](https://gagamblinghelpline.org/terms/house-edge/)

The expected loss per unit staked, fixed by the gap between the prize a game pays and the prize a fair game would pay.

per unit staked

HOUSE ADVANTAGE

## I

[Implied probability](https://gagamblinghelpline.org/terms/#I)

The probability a quoted price corresponds to, found by taking the reciprocal of the decimal price.

ODDS AND PRICES

[Independent events](https://gagamblinghelpline.org/terms/#I)

Events whose probabilities are unaffected by one another, so past results carry no information about the next trial.

PROBABILITY

## J

[Jackpot](https://gagamblinghelpline.org/terms/#J)

A prize accumulating from a fixed share of each amount staked until a stated result occurs.

per unit staked

GAMES AND RULES

## K

[Kelly criterion](https://gagamblinghelpline.org/terms/#K)

A staking formula maximising the long-run growth rate of funds; it returns a stake of zero whenever the expected value is negative.

VARIANCE AND STREAKS

## L

[Law of large numbers](https://gagamblinghelpline.org/terms/#L)

The result that the observed proportion of an outcome approaches its probability as trials rise, while the absolute gap need not shrink.

PROBABILITY

[Long run](https://gagamblinghelpline.org/terms/#L)

The count of trials at which expected loss grows large relative to the spread of results around it.

VARIANCE AND STREAKS

## M

[Margin](https://gagamblinghelpline.org/terms/#M)

The share of the total staked on a market that its prices are expected to retain once every outcome is covered.

per unit staked

ODDS AND PRICES

[Martingale](https://gagamblinghelpline.org/terms/#M)

A staking pattern doubling the stake after each loss; it changes the distribution of results and leaves the expected value unchanged.

VARIANCE AND STREAKS

## N

[Negative expectation](https://gagamblinghelpline.org/terms/#N)

A bet whose probability-weighted average outcome is a loss, which is the condition of every commercially offered game of chance.

HOUSE ADVANTAGE

## O

[Odds](https://gagamblinghelpline.org/terms/#O)

A statement of the ratio between the ways a result can fail and the ways it can occur, or of the price paid for it.

ODDS AND PRICES

[Overround](https://gagamblinghelpline.org/terms/#O)

The amount by which the implied probabilities of all outcomes in a market exceed one hundred per cent.

per market

ODDS AND PRICES

## P

[Pari-mutuel](https://gagamblinghelpline.org/terms/#P)

A pool system combining all stakes, deducting a fixed share, and dividing the remainder among winning tickets.

per unit staked

LOTTERIES AND DRAWS

[Par sheet](https://gagamblinghelpline.org/terms/#P)

The internal specification of a game listing every symbol weight, every prize, and the return the two together produce.

GAMES AND RULES

[Permutation](https://gagamblinghelpline.org/terms/#P)

An arrangement in which order matters, counted before dividing out the orderings to reach a combination.

LOTTERIES AND DRAWS

[Probability](https://gagamblinghelpline.org/terms/#P)

The proportion of equally likely outcomes producing a stated result, written as a number between zero and one.

PROBABILITY

## Q

[Quinella](https://gagamblinghelpline.org/terms/#Q)

A pool bet requiring the first two finishers in either order, settled from the pari-mutuel pool for that bet type.

LOTTERIES AND DRAWS

## R

[Random number generator](https://gagamblinghelpline.org/terms/#R)

The mechanism selecting a game's outcome; a certified one produces results passing tests for uniformity and independence.

GAMES AND RULES

[Regression to the mean](https://gagamblinghelpline.org/terms/#R)

The tendency for an extreme run of results to be followed by results nearer the average, with no correcting force involved.

VARIANCE AND STREAKS

[Return to player](https://gagamblinghelpline.org/terms/#R)

The proportion of total amounts staked a game returns as prizes over the long run; its complement is the house edge.

per unit staked

HOUSE ADVANTAGE

## S

[Sample space](https://gagamblinghelpline.org/terms/#S)

The complete set of outcomes a trial can produce; one die has six, two dice have thirty-six.

PROBABILITY

[Standard deviation](https://gagamblinghelpline.org/terms/#S)

The typical distance of a result from the average, growing with the square root of the count of trials.

VARIANCE AND STREAKS

[Streak](https://gagamblinghelpline.org/terms/#S)

A run of identical consecutive results, whose probability falls geometrically with length but which is ordinary across many trials.

VARIANCE AND STREAKS

## T

[Trial](https://gagamblinghelpline.org/terms/#T)

One repetition of a game or bet, the unit in which counts, probabilities and expected values are stated.

PROBABILITY

[True odds](https://gagamblinghelpline.org/terms/#T)

The odds corresponding exactly to a result's probability, against which the odds actually paid are compared.

HOUSE ADVANTAGE

[Turnover](https://gagamblinghelpline.org/terms/#T)

The total amount staked over a period, which is the base a per-unit-staked figure is multiplied by.

per unit staked

HOUSE ADVANTAGE

## U

[Unit](https://gagamblinghelpline.org/terms/#U)

The stake size a figure is expressed in; percentages here are stated per unit staked unless another base is named.

HOUSE ADVANTAGE

## V

[Variance](https://gagamblinghelpline.org/terms/variance/)

The average squared distance of results from their mean; its square root is the standard deviation.

VARIANCE AND STREAKS

[Virtual reel](https://gagamblinghelpline.org/terms/#V)

A mapping assigning unequal numbers of internal positions to the visible symbols of a reel, setting their true probabilities.

GAMES AND RULES

[Volatility](https://gagamblinghelpline.org/terms/#V)

How widely a game's results spread around its return, set separately from the return itself.

VARIANCE AND STREAKS

## W

[Wager](https://gagamblinghelpline.org/terms/#W)

An amount staked on a stated outcome under stated terms.

HOUSE ADVANTAGE

## X

No entry in this index begins with X.

## Y

No entry in this index begins with Y.

## Z

[Zero](https://gagamblinghelpline.org/terms/#Z)

The pocket or pockets on a wheel belonging to neither even-money group, and the entire source of the wheel's edge.

HOUSE ADVANTAGE