Online casino vocabulary can be confusing for newcomers and even for experienced players who have never looked up a term they have seen used repeatedly. This glossary defines the most important terms used in online casino games, bonus promotions, and responsible gambling in plain English. Terms are grouped by category for easy reference.
Game Mechanics and Mathematics
Return to Player (RTP)
RTP is the percentage of all money wagered on a game that is paid back to players over a very large number of rounds. An RTP of 96% means the game returns £96 for every £100 wagered on average across millions of spins or rounds. RTP is calculated over millions of rounds and does not predict results in any individual session. UKGC-licensed sites are required to display RTP for their slot games.
House Edge
The house edge is the flip side of RTP: it is the percentage of each wager the casino expects to retain as profit over the long run. House edge = 100% minus RTP. A slot with 96% RTP has a 4% house edge. Blackjack with basic strategy has a house edge of approximately 0.5%.
Variance (Volatility)
Variance describes how results are distributed around the expected average. High-variance games pay infrequently but in larger amounts; low-variance games pay more often but in smaller amounts. The RTP of two games with identical RTPs can feel very different if one is high-variance and the other is low-variance.
Random Number Generator (RNG)
The RNG is the software algorithm that determines the outcome of each game round at an online casino. A properly implemented and independently certified RNG produces results that are genuinely random and cannot be predicted or manipulated by the casino or the player.
Expected Value (EV)
Expected value is the mathematical average return of a bet over many repetitions. A bet with negative EV returns less than the stake on average — which describes all standard casino bets. A £10 bet at European roulette has an EV of −£0.27 (the house edge applied to the stake).
Bonus and Promotion Terms
Welcome Bonus
A welcome bonus is an offer made to new players, typically on their first deposit. Common formats include deposit match bonuses (e.g., 100% match up to £100, meaning a £100 deposit receives an additional £100 in bonus funds) and free spins packages.
Wagering Requirement (Playthrough)
The wagering requirement specifies how many times a bonus amount must be staked before it can be withdrawn. A £50 bonus with a 30x wagering requirement means the player must place £1,500 in bets before cashing out any winnings derived from the bonus. Wagering requirements are the single most important term to check on any bonus offer.
Game Weighting
When a bonus has a wagering requirement, different game types often contribute at different rates towards completing it. Slots might contribute 100%, blackjack 10%, and roulette 5%. Playing a game with 5% contribution means you need 20 times more bets to clear the same requirement.
Sticky Bonus
A sticky (or non-cashable) bonus is one that cannot itself be withdrawn — only winnings generated from it can be cashed out. The bonus funds disappear when the wagering requirement is completed or when you withdraw.
Free Spins
Free spins are a type of bonus that lets players spin a specific slot game a set number of times without using their own funds. Winnings from free spins typically carry their own wagering requirement before withdrawal is permitted. The individual spin value may be fixed (e.g., £0.10 per free spin).
No-Deposit Bonus
A no-deposit bonus is an offer awarded without requiring a deposit — typically a small sum of bonus money or a handful of free spins. Wagering requirements on no-deposit bonuses are often higher than on deposit bonuses, and maximum withdrawal limits usually apply.
Maximum Bonus Win Cap
Many bonuses carry a cap on how much can be won from the bonus funds. For example, a free spins offer might have a maximum win of £50, meaning winnings beyond £50 are forfeit regardless of what was generated during play.
Account and Payment Terms
KYC (Know Your Customer)
KYC refers to the identity verification process that licensed operators must conduct. Players are typically required to submit documents proving identity (passport or driving licence), address (utility bill or bank statement), and in some cases source of funds. KYC is a legal requirement under UK anti-money laundering regulations.
Source of Funds
Source-of-funds verification is requested by operators when a player deposits significant amounts. Players may be asked to show payslips, bank statements, or other evidence that their gambling funds come from legitimate income. This is an AML requirement under UKGC licensing conditions.
E-wallet
An e-wallet is a digital payment service (such as PayPal, Skrill, or Neteller) that acts as an intermediary between a bank account and a casino. E-wallets are widely used by UK casino players for faster deposits and withdrawals. Note that some bonuses exclude deposits made via e-wallets.
Pending Period
Some operators apply a pending period to withdrawal requests — typically 24 to 72 hours — during which the withdrawal can be cancelled and funds returned to the account. This window exists to allow problem gambling reversals; some operators extend it intentionally to encourage continued play, which is a practice the UKGC has scrutinised.
Responsible Gambling Terms
Self-Exclusion
Self-exclusion is a voluntary request to be blocked from gambling at one or more operators. In the UK, GAMSTOP provides national online self-exclusion covering all UKGC-licensed sites with a single registration.
GAMSTOP
GAMSTOP is the UK's free national online self-exclusion scheme. Registering at GAMSTOP.co.uk blocks access to all UKGC-licensed online gambling sites for a minimum of six months and up to five years.
Deposit Limit
A deposit limit is a player-set cap on how much money can be added to a casino account in a day, week, or month. UKGC regulations require operators to offer this tool and to apply a cooling-off period before any limit increase takes effect.
Reality Check
A reality check is an on-screen notification that appears at player-selected intervals during a session. It typically displays the session duration and the player's net win or loss, prompting reflection about whether to continue.
GamCare
GamCare is the UK's leading provider of free, confidential gambling support. Its National Gambling Helpline operates 24/7 on 0808 8020 133. Services include telephone and live chat counselling, an online forum, and referrals to specialist treatment.
Game-Specific Terms
Blackjack: Soft vs Hard Hand
A soft hand in blackjack contains an ace counted as 11 (e.g., ace-7 = soft 18). A hard hand contains no ace or an ace counted as 1. The distinction matters because soft hands cannot bust on a single hit.
Roulette: La Partage
La Partage is a French roulette rule that returns half the stake on even-money bets when zero lands. It reduces the house edge from 2.7% to 1.35% and is the most player-friendly variant of roulette widely available online.
Slots: Payline
A payline is a line across the slot reels on which a winning combination of symbols must land to trigger a payout. Traditional slots had a single horizontal payline; modern video slots often have anywhere from 10 to 1,024 or more paylines, sometimes called "ways to win."
Slots: Scatter Symbol
A scatter symbol in a slot game triggers its effect regardless of whether it lands on a payline — it simply needs to appear on the reels in sufficient quantity (usually three or more) to trigger a bonus feature, free spins round, or direct payout.
Slots: Wild Symbol
A wild symbol substitutes for other standard symbols to help form winning combinations, similar to a joker in card games. Some wilds have additional properties — expanding wilds fill an entire reel, sticky wilds remain in place for multiple spins.
Progressive Jackpot
A progressive jackpot is a prize pool that grows every time a player makes a qualifying stake, with a small percentage of each bet contributing to the jackpot. It can be triggered randomly or through a specific in-game event. Progressive jackpots often reach six or seven figures before being won. Their RTP is typically lower than standard slots, often in the 88% to 93% range.
Live Casino
Live casino games are broadcast in real time from a studio with real dealers, physical cards, and real wheels. Players participate via a video stream interface. Common live titles include live blackjack, live roulette, live baccarat, and live game shows.
Conclusion
Understanding the vocabulary of online casino gaming puts you in a stronger position to evaluate games, read bonus terms critically, and use the responsible gambling tools available to you. The terms in this glossary are the building blocks of informed casino play. Returning to reference it when you encounter unfamiliar terminology — particularly in bonus terms and conditions — will help you avoid misunderstandings and make better decisions about where and how you gamble.