Slots Glossary: Every Term Explained
Slot machines come with their own vocabulary, and knowing the terms helps make sense of how they work. This glossary highlights the most common terminology found in both online and land-based formats.
From classic three-reel formats to modern feature-rich designs, the entries below cover the key components, symbols, bonus elements, and return structures that define slot gameplay.
Understanding the Terms of Mechanics
The foundation of any slot game lies in its structure and the way outcomes are determined.
This section explains the main terms used to describe how slots are built and how they function.
Reels
The vertical spinning columns of a slot machine are known as reels, each holding a set of symbols. Classic machines typically feature three reels, while most modern video slots use five or more. The arrangement of symbols on the reels after a spin determines winning combinations (otherwise called wins).
Symbols
Within any slot, symbols are the icons that land on the reels and determine outcomes. Most slots include a mix of lower-paying symbols, often represented by card values, and higher-paying ones tied to the game’s theme. In addition to these, special symbols like wilds and scatters introduce bonus functions or unlock features (discussed in detail later).
While classic machines relied on simple designs like fruits, bars, bells, and sevens, today’s slots often expand on this with elaborate themes and detailed graphics, even when inspired by traditional three-reel setups.
Paylines
These are the lines across the reels that determine where matching symbols must land to trigger a win. These lines can run horizontally or diagonally, and in many modern games, may even follow intricate zigzag shapes. Classic machines usually had a single central line, while modern slots can feature dozens or more.
Ways to Win
In this system, winning combinations are formed by matching symbols on adjacent reels, usually from left to right, rather than relying on fixed paylines. A common format is 243 ways to win, typically in five-reel slots, though some games extend this into the thousands.
This setup removes the need to track specific paylines, as any left-to-right sequence across consecutive reels counts as a win.
Adjustable Paylines
Some slot games allow the number of active paylines to be changed before a spin. Reducing the number of paylines lowers the total bet size. Activating more lines increases the wager and covers a greater range of possible winning positions on the reels.
Rows
These are the horizontal sections on a slot machine where symbols land across the reels. Classic slots often had three rows, while modern video slots may feature four or more, creating larger grids with more possible outcomes per spin.
Spin
A spin is the action that sets the reels in motion, activated by a button on a machine or a digital control in online slots. Once the reels stop, the final arrangement of symbols determines whether a winning combination or feature is triggered.
Bet
The bet is the amount of money placed on a single spin. Many slots allow it to be adjusted through settings like coin value or bet level. In some games, the total bet also depends on the number of active paylines or ways to win. A higher bet increases the overall stake and raises the potential size of returns.
Coin Value
This refers to the amount of money each coin or credit represents in a slot game. Changing it adjusts how much the bet and any returns are worth in real money. For example, setting the coin value to $0.10 means a 10-coin bet equals $1.
Paytable
The paytable is the information panel that explains how a slot game awards returns. It lists all symbols, their values, the rules for forming winning combinations, and details of any special features or bonus rounds.
RTP
Short for Return to Player, this percentage shows how much a slot is designed to return over time. For example, a game with a 96% RTP is expected to give back $96 for every $100 wagered, measured across a long-term average rather than individual sessions.
RTP is calculated through extensive simulations of millions of spins, ensuring statistical accuracy. While it gives an indication of a slot’s overall return potential, it does not predict short-term outcomes, which remain random.
Volatility
This term describes the risk level of a slot game based on how often and how much it tends to return. Low-volatility slots typically produce smaller but more frequent outcomes, while high-volatility slots offer larger returns that occur less often. Medium volatility sits between the two.
Developers assign volatility during testing, and while it isn’t usually stated as a percentage like RTP, it provides a general expectation of a game’s return patterns.
Balance
The balance refers to the total amount of money available in a slot session. It decreases with each bet placed and increases with any returns from winning combinations or bonus features.
Bonus Round
A bonus round is a special feature within a slot that takes place outside the base reels. It may involve free spins, pick-and-win games, wheel bonuses, or other interactive elements.
These rounds are designed to add variety to the gameplay and can sometimes award larger returns than the base game.
Jackpot
A jackpot is the top prize available in a slot game. In some slots, this is a fixed amount determined by the game’s paytable. Others feature progressive jackpots, which increase over time as a small portion of each wager is added to a shared prize pool.
Progressive jackpots can be limited to a single game or linked across multiple machines and online networks, sometimes reaching large amounts before being won.
Cascading Reels
Sometimes called tumbling reels, this mechanic replaces winning symbols with new ones that drop into the empty spaces. This can lead to multiple wins from a single spin, continuing until no new matches appear.
Cluster Pays
This system awards returns when groups of matching symbols land adjacent to each other, either vertically or horizontally. Unlike traditional paylines, there is no need for symbols to follow a set line, as clusters of a certain size trigger a return.
Terms for Special Symbols & Features
In addition to the basic mechanics, many slots include special symbols and bonus features that add variety to the gameplay. This section explains the most common ones, from wilds and scatters to unique mechanics like Megaways and mystery symbols.
Wild Symbol
A wild symbol substitutes for other standard symbols on the reels to help complete wins. Some slots feature different types of wilds with additional properties (covered in the sections below), but the basic function is to act as a substitute and improve the chances of forming a return.
Sticky Wild
A sticky wild remains in place on the reels for multiple spins once it appears. This increases the likelihood of additional winning combinations during the spins it stays active.
Stacked Wild
A stacked wild appears in a vertical stack, covering part or all of a reel. By occupying multiple symbol positions at once, it increases the potential for larger winning combinations.
Expanding Wild
An expanding wild grows to cover an entire reel when it lands. This feature boosts the chance of creating multiple wins in a single spin.
Walking Wild
A walking wild shifts to a new reel position on each spin until it disappears from the grid. This movement can extend the feature across several spins, allowing additional winning combinations to form.
Multiplier Wild
A multiplier wild (like normal wilds) substitutes for standard symbols and increases the value of any win it helps create. The multiplier can be fixed, like 2x, or vary depending on the game’s design.
Scatter
A scatter is a special symbol that usually triggers bonus features or free spins when a required number appears on the reels. Unlike standard symbols, scatters can award wins or activate features regardless of their position on the grid.
Bonus Symbol
A bonus symbol is used to unlock a specific feature within a slot, often leading to a dedicated bonus round. The number of bonus symbols required to trigger the feature varies by game.
Multipliers
These features increase the value of a win by a set factor. For example, a 3x multiplier triples the amount won. They can appear on their own, during base game spins, inside bonus rounds, or combined with special symbols like wilds (as mentioned above).
Free Spins
The free spins feature allows the reels to spin without deducting from the balance. It is usually triggered by scatter symbols and often includes added elements like multipliers or expanding wilds.
Pick-and-Win Bonus
A pick-and-win bonus presents a set of hidden options, like boxes or symbols, that can be chosen to reveal instant prizes. Rewards often include credits, multipliers, free spins, or access to further bonus rounds.
Wheel Bonus
A wheel bonus involves spinning a prize wheel to determine an award. The wheel is divided into segments that can grant credits, multipliers, free spins, or entry into another bonus feature.
MEGAWAYS
This mechanic, introduced by Big Time Gaming, changes the number of symbols that appear on each reel with every spin. Because the reel setup is different each time, the number of possible winning combinations varies, often reaching into the tens or even hundreds of thousands.
Nudge Feature
The nudge feature allows a reel to shift by one or more positions after stopping, potentially turning a near miss into a winning combination. Nudges may occur randomly or as part of a triggered bonus.
Mystery Symbols
Such symbols appear as identical icons that transform into a randomly chosen symbol once the reels stop. In many games, they all reveal the same symbol at once, raising the chances of landing a win.