Casino Glossary: Definitions With the Numbers Behind Them
Definitions here are written to be checkable. Where a term has a number attached — a house edge, a payout ratio — the number is derived from published game rules, and the derivation is shown.
The terms that decide how much you lose
House edge
The share of every stake an operator retains on average over a very large number of rounds. European roulette is 2.70% because the wheel has 37 pockets and pays a straight-up number at 35 to 1: the missing units are the edge. It applies to turnover, not to your deposit or your net position.
Return to player (RTP)
The same quantity from the other side: a 96% RTP is a 4% house edge. It is a design parameter measured across millions of simulated rounds, which is why it says nothing about an evening.
Volatility (variance)
How returns are distributed around that average. Two games with identical RTP can pay small amounts often or large amounts rarely. Volatility determines how quickly a bankroll is likely to be exhausted; it does not change the edge.
Turnover
The total staked, counting every round, not the amount deposited. This is the quantity the house edge multiplies, and the reason session length matters more than deposit size.
Bonus terminology
Wagering requirement
The turnover needed before bonus funds can be withdrawn, expressed as a multiplier. "40× bonus" on a 100 bonus means 4,000 of turnover. At an average 4% edge that turnover costs about 160 in expectation, which is more than the bonus.
Game contribution
The percentage of a wager that counts toward wagering. Slots often contribute 100%, table games 10% or less, and some games nothing at all. A requirement that looks reachable on slots can be practically impossible on roulette.
Maximum bet while bonus is active
A cap, commonly around 5, that applies until wagering is complete. Exceeding it is one of the most frequent reasons for a forfeited bonus, and it is usually buried in the terms.
Sticky bonus
A bonus that can never itself be withdrawn — only winnings generated from it. The opposite is a cashable bonus.
Verification and account terms
KYC (Know Your Customer)
Identity verification required by anti-money-laundering rules. Usually triggered at first withdrawal, which is why the process is so often experienced as a withdrawal delay.
Source of funds check
A further step requiring documentation of where money came from, typically for larger amounts. It is a legal obligation on the operator rather than a discretionary demand.
Closed-loop withdrawal
The rule that money returns by the method it arrived on, at least up to the amount deposited. Also an anti-money-laundering requirement.
Self-exclusion
A binding account closure for a fixed term that cannot be lifted early. Distinct from a cooling-off period, which is shorter, and from a deposit limit, which restricts rather than closes.
Licensing terms
Licence number
The identifier that makes a licence claim checkable. A jurisdiction name alone — "licensed in Curaçao" — identifies nothing, because it names neither the company nor the domains covered.
Domain list
The set of addresses written into a licence record. This is the part that decides whether the site in your address bar is covered. An address absent from the record is, for complaint purposes, an unlicensed site.
B2C licence
A licence to offer gambling directly to players, as opposed to B2B, which covers supplying software to other operators.
Game mechanics
RNG (random number generator)
The component that resolves each round independently of the last. Independence is why no pattern-based method can work, and why the machine has no memory of your session.
Provably fair
A cryptographic procedure allowing a player to verify that a result was fixed before the bet and unchanged afterwards. It proves the integrity of the draw and says nothing about the house edge.
Near miss
A losing outcome displayed as almost winning. The result was determined at the start of the spin; the presentation is a design choice.
Loss disguised as a win (LDW)
A round returning less than it cost while celebrating like a win — staking 1.00 and receiving 0.40. A documented feature of multi-line slot design.
Overround (margin, vigorish)
In betting markets, the amount by which implied probabilities exceed 100%. Prices of 1.90 and 1.90 imply 52.6% each, totalling 105.3%, so the margin is 5.3%.