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Gambling words and phrases explained

This section explains some of the terms and phrases used in gambling. Understanding how gambling works, especially in relation to odds, probability, house edge and randomness, can help protect people from gambling harms. Being able to make an informed choice about whether to gamble by understanding the likelihood of a positive outcome can help you to not spend more than you can afford to lose, and help with rational thinking if you feel tempted to chase your losses. 

What are the "odds"?

The odds are the probability, or the likelihood, of a specific outcome or event taking place, for example whether a team will win or match or whether six numbers in a lottery draw will match the selection made by a lottery player. To work out the odds, you divide the number of specific outcomes with the number of possible outcomes.

For example, if you were rolling a dice and wanted the number three to come up, there is only one specific outcome; at the same time, there are six possible outcomes because the dice could land on one, two, three, four, five or six. So the probability of you rolling a three is 1 in 6.

What is the "House Edge"?

In gambling, the "odds" are the chances a person has of winning a bet, but these always work against that person.

The "house" refers to the people who offer the bet (the casino, bookmaker, slot machine owner, etc.) and they always have the "edge". This means that the designers of the machine or game make sure that it works in their favour and they will always make money overall.

In every betting game, the odds are against the player. Every person who hits the jackpot on a slot machine is actually winning money that previous players lost. The longer you gamble, the more likely it is that you will lose money, because the odds are against you. Many problem gamblers have the false belief that they will be able to "beat the system" but over time they'll lose money, probably an awful lot of it.

The odds of winning the jackpot on a six-number lottery draw like the UK National Lottery are about 1 in 45 million. Think of it like this: your friend Dave lives somewhere in England and you want to call him at home but don't have his number. If you try reaching him by dialling one of 42 million phone numbers, your odds of getting his number right on the first try are better than the odds of winning the lottery jackpot.

What does "Return to Player" mean?

Return to Player (RTP) is the term that gambling businesses use to describe the percentage of all the wagered money that a gambling machine or game will pay out over time. RTP is calculated over the long term, so over a number of months, rather than being a calculation of short term (e.g. session, daily or even weekly) payout. An 80% RTP does not mean that within that gambling session, or for that particular gambler, 80% of what has been wagered will be returned to them in winnings. In the short term, the return may be vastly different and can often be nothing, so you should only ever bet with money you can afford to lose.

What is skill and what is chance?

Some forms of gambling are down to chance, and some may involve some skill as well as chance. Here are some examples:


Lottery, Euromillions etc
Slot machines

Skill (at least partially):

Sports betting

In chance-based games, each outcome is as likely as all of the others to happen, so a number 6 ball dropping in a bingo draw is as likely as a number 22. If a flipped coin landed on heads several times in a row, it's easy to think that it has to come up tails on the next flip. However, the coin doesn't "remember” what it has landed on before in the same way that it doesn't "decide” what to land on next.

No matter what has happened already, the probability of it landing on heads or tails is always 50/50. The result of a rolled dice or flipped coin is unknown and unpredictable, so we can say that the outcome is random.

This applies to whether a roulette wheel hits red or black, odds or even.

It applies to whether the same number will come up in the National Lottery if it came up for the past 3 weeks in a row - it is just as likely to appear as it is not.

What does "Random" mean?

Random means that each possible outcome has the same chance, or probability, of occurring.

For example:

When you roll a dice, the probability of rolling a two is the same as the probability of rolling a six, which is the same probability of rolling any of the other numbers. So you could say that the chance of rolling a specific number is one in six.

When you flip a coin, the probability of it landing on heads is the same as the probability of it landing on tails, so you could say that it has a 50% chance or it's 50/50.

Remember: despite what you might think, you can't work out, predict or control an outcome that's based on chance and randomness – people who try to do this often lose a lot of money. They might win now and then, but this is also down to chance. Thinking that you can beat the system can cause big problems.

Can you spot a pattern in a random game?