This glossary explains the words you meet on a slot machine screen, in a casino, and in articles about slots, in plain language. A few of them matter more than the rest for your wallet: RTP, hit frequency, volatility, paylines and total bet. The rest describe features and parts of the machine. Each entry says what the term means and, where it helps, what it means for the cost of playing.
Terms are grouped by topic so you can read a section at a time. Where a term is defined in a regulation, we use the regulation’s meaning, and we link to the full guide when a term deserves one. The calculations in the examples are our own.
The money and the maths
RTP (return to player). The percentage of money wagered that a game pays back over a very long run. A 90% RTP game keeps $10 of every $100 wagered on average. See how slot machines work.
Theoretical payout. The regulatory name for the long-run return of a game. Nevada requires it to be at least 75 percent, and New Jersey requires at least 83 percent.
House edge. The share the casino keeps, which is 100% minus the RTP. A 90% RTP game has a 10% house edge.
Hold. The share of the money wagered that the casino keeps. The theoretical hold equals the house edge. The actual hold is what happened over a real period, which can differ because of luck.
Hit frequency. How often a spin pays anything, including spins that pay less than the bet. A 21% hit frequency means about one spin in five pays.
Volatility (variance). How widely results spread around the average. High volatility means long dry runs and occasional large wins. See how to choose a slot.
Standard deviation. A number that measures how spread out results are. In our examples, a standard deviation of 2.26 coins per spin describes a steady game and 11.05 describes a volatile one.
Expected value. The average result per bet over many repetitions. For a slot it is negative, equal to minus the house edge times the bet.
Wager (total bet). The full amount you stake on one spin. It is the line bet times the number of lines, plus any extra bets. This is the number that sets your cost per hour.
Credit. The unit the machine uses to track your balance. A credit has a denomination, such as one cent or one dollar, which sets its value.
Denomination. The value of one credit, for example 1 cent or 25 cents. A low denomination does not mean a low total bet when many lines are played.
Bankroll. The money you set aside for a session. See our session and bankroll plan.
Gambler’s fallacy. The mistaken belief that a result is “due” because it has not happened recently. See slot machine myths.
How the machine decides
Random number generator (RNG). The program that produces numbers continuously and picks the result of each spin. The reels display a result that was already chosen.
Virtual reel. The list of positions the RNG chooses from. It can be longer than the visible reel, so a symbol can have a different chance from what the display suggests.
Reel strip. The ordered list of symbols on a reel, whether a physical band or a digital list.
Stop. One position on a reel where it can come to rest.
Paytable (pay table). The list of what each combination pays. Our pay table guide explains how to read one.
Payline. A path across the reels that a winning combination must follow. You pay for each line you play.
Ways to win. A system that replaces paylines. A win forms from matching symbols on adjacent reels, and the number of ways is the product of the positions on each reel. A 5-reel, 3-row game has 243 ways.
Cluster pay. A system where a win is a group of matching symbols that touch each other on a grid.
Cascade (tumble). A feature where winning symbols vanish and new ones fall into place, which can create several wins from one bet.
Near miss. A result that looks close to a big win. It carries no extra meaning, because the outcome was chosen before the reels stopped.
Alternate animation. A different way of showing the same result. New Jersey allows it only if it does not change how often top symbols appear and the display is not misleading.
Symbols and features
Wild. A symbol that substitutes for other symbols to complete a winning combination, usually not for scatters or bonus symbols.
Scatter. A symbol that pays or triggers a feature wherever it lands, not only on a payline.
Bonus symbol. A symbol that starts a separate bonus game.
Multiplier. A factor, such as 2x or 5x, that increases a win.
Free spins. Spins awarded without charging your balance, usually triggered by scatters. New Jersey requires the number remaining to be displayed.
Respin. An extra spin of some or all reels, often awarded by a feature.
Hold and win. A feature where special symbols lock in place while a limited number of respins try to land more.
Pick bonus. A feature where you choose items on screen to reveal prizes.
Expanding wild. A wild that grows to fill its whole reel.
Sticky wild. A wild that stays in place for several spins.
Gamble feature. An option to risk a win on a further choice. New Jersey allows it only if the award can grow with continued play, and the optimal strategy must be disclosed if it affects the return.
Bonus buy (feature buy). An option to pay a multiple of your bet to start a feature straight away. The cost per spin is much higher.
Auto-play. A setting that spins repeatedly without you pressing the button. It speeds up the pace and raises the amount wagered per hour.
Jackpots
Progressive jackpot. A prize that grows with bets until it is won. See how progressive jackpots work.
Reset amount. The starting value of a progressive jackpot after it has been won.
Incrementation rate. The rate at which a progressive meter grows with each bet.
Wide-area progressive. A jackpot shared by machines in many casinos through a central server.
Meter. A counter. Machines have many, including the display meter that shows the current progressive jackpot.
Machines and places
Video slot. A slot that shows its reels on a screen, usually with many lines and features.
Classic (three-reel) slot. A slot with three reels, often one payline and a short pay table.
Video poker. A machine where you hold and discard cards to make the best poker hand. See video poker pay tables.
Fruit machine. The common UK name for a slot-style gaming machine.
Pokies. The common name for slot machines in Australia and New Zealand.
VLT (video lottery terminal). A machine run under a government lottery system in some places.
TITO (ticket in, ticket out). A system where machines accept and print paper tickets instead of coins.
Malfunction void. A notice, required by New Jersey on each machine, that a malfunction voids all pays.
Safer play
Reality check. A message at set intervals showing time played or money spent.
Deposit limit. A cap on how much you can add to an account in a period.
Self-exclusion. A formal way to bar yourself from gambling at a venue or site. See self-exclusion and blocking tools.
Loss disguised as a win. A spin that pays less than the total bet but plays the sounds and lights of a win. It counts toward hit frequency while your balance falls.
Chasing losses. Raising bets or playing longer to recover money already lost. It raises the amount wagered and the average cost.
Terms that sound alike but are not the same
A few pairs of terms get mixed up, and the difference affects how you read a game.
- RTP and hit frequency. RTP is how much of your money comes back over the long run. Hit frequency is how often something comes back at all. A game can have a high hit frequency and a low RTP if most hits are tiny.
- Volatility and RTP. RTP is the average. Volatility is the spread around it. Two games can share an RTP and have very different volatility.
- Hold and house edge. House edge is the theory, and hold is what a casino actually kept over a period. A single machine’s hold in a week can be far from its edge.
- Denomination and total bet. The denomination is the value of one credit. The total bet is credits per line times lines. A penny denomination can still produce a bet of a dollar or more.
- Payline and way. A payline is a fixed path you pay for. A way is any adjacent-reel route, and you pay for all of them in the base bet.
- Wild and scatter. A wild helps complete a line, and a scatter pays or triggers a feature anywhere on the screen.
Keeping these apart makes pay tables and reviews much easier to read, because many of the claims you see online rely on blurring them.
If a term here describes something you recognise in your own play, such as chasing losses, step back and read the Safer play toolkit. If gambling is causing harm, visit our get help page.
Where should you go next?
To see these terms in use, read how slot machines work. To understand the types behind the features, read types of slot machines. And to see what regulators require, read are slot machines rigged.