Reference library / Game mechanics

Slot Mechanics Glossary: Reels, Wilds and Cascades

Explore the mechanics behind modern slot games: what each feature actually changes, what it does not guarantee, and which verified game profiles use it.

Paylines and ways to win

A payline is a specified sequence of positions used to evaluate symbol combinations. “Ways to win” and pay-anywhere systems use different evaluation rules. A five-reel display alone does not tell you how prizes are determined.

Wild and scatter

Wild symbols typically substitute for specified paying symbols but may have exclusions. Scatter symbols usually trigger or pay based on their own conditions. Some games use collect symbols instead. Each title’s rules control the details.

Cascades and tumbling reels

After qualifying wins, symbols can be removed and replaced without starting a new paid spin. The mechanic is sometimes called tumble, cascade or avalanche. Its effect on multipliers and feature rounds varies by game.

Expanding symbols

An expanding wild or special symbol may fill an entire reel or specified positions after triggering. Starburst and Book of Dead illustrate different versions.

Megaways and variable structures

Variable-reel-height systems can produce changing ways to win; the number of possible configurations should never be equated to a guarantee of favorable payouts. Named branded mechanics may be subject to intellectual property rights.

Using the glossary

Read the official paytable first. This glossary defines general ideas, not a contractual description of every individual game. For special features, see free spins explained.

Explore mechanics

Every mechanic is explained separately. A profile appears in a mechanic collection only when its editor has assigned that term.

Game mechanic

Bonus Buy; Scatter Symbols

An explanation of this mechanic and its rules.

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Game mechanic

Cascading Reels

Cascading reels, also called tumbling or avalanche features in some games, remove symbols from a winning result and replace them with new symbols without requiring a new paid spin. The name…

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Game mechanic

Cascading Reels; Free Spins; Bonus Buy; Multipliers; Wild Symbols

An explanation of this mechanic and its rules.

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Game mechanic

Cluster Pays

Cluster Pays slots award wins for qualifying groups of adjacent matching symbols instead of relying only on traditional fixed paylines. What constitutes adjacency and how large a cluster must be are…

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Game mechanic

Cluster Pays; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Cluster Pays; Free Spins; Bonus Buy; Collect Symbols; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Cluster Pays; Free Spins; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Cluster Pays; Multipliers; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Expanding Symbols

Expanding symbols can cover additional symbol positions under specified conditions. Expansions may create new combinations, change the way wins are evaluated, or operate only in special rounds.How it worksA triggering symbol…

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Game mechanic

Expanding Wilds; Respins; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Feature Buy / Bonus Buy

Feature-buy options, where legally available, allow a player to purchase direct access to a defined game feature at a specified cost. Availability depends on the particular software configuration and jurisdiction. A…

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Game mechanic

Free Spins

Free spins are feature rounds that can be triggered by symbols or other conditions under a game’s published rules. They are part of the game mathematics; the word free does not…

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Game mechanic

Free Spins; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Free Spins; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Free Spins; Expanding Symbols; Wild Symbols; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Free Spins; Expanding Wilds; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Free Spins; Hold & Win; Bonus Buy; Collect Symbols

An explanation of this mechanic and its rules.

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Game mechanic

Free Spins; Multipliers; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win / Respin Features

Hold-and-win and similar respin features retain certain symbols on the game grid while offering additional spins or chances to fill positions. The precise rules differ between products and should not be…

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Game mechanic

Hold & Win / Respins

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Bonus Buy; Collect Symbols; Wild Symbols

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Bonus Buy; Jackpots

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Bonus Buy; Jackpots; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Bonus Buy; Multipliers; Jackpots

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Bonus Buy; Wild Symbols; Jackpots

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Expanding Wilds; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Expanding Wilds; Jackpots

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Free Spins; Trueways; Jackpots

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Jackpots; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Trueways; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Hold & Win; Trueways; Jackpots

An explanation of this mechanic and its rules.

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Game mechanic

Jackpots; Respins; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Megaways

Megaways is a variable-reel system in which the number of symbols visible on a reel can change from spin to spin. The total number of possible ways to win therefore changes…

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Game mechanic

Megaways; Cascading Reels; Free Spins; Bonus Buy; Wild Symbols

An explanation of this mechanic and its rules.

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Game mechanic

Paylines; Gamble Feature

An explanation of this mechanic and its rules.

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Game mechanic

Pays Anywhere; Cascading Reels; Free Spins; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Pays Anywhere; Free Spins

An explanation of this mechanic and its rules.

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Game mechanic

Pays Anywhere; Free Spins; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Pays Anywhere; Free Spins; Bonus Buy; Multipliers; Cascading Reels

An explanation of this mechanic and its rules.

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Game mechanic

Pays Anywhere; Hold & Win; Multipliers; Bonus Buy

An explanation of this mechanic and its rules.

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Game mechanic

Pays Anywhere; Wild Symbols; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Scatter Symbols

Scatter symbols often award features or prizes based on the number appearing in a game result rather than on a conventional payline. The term alone does not define a standard payout…

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Game mechanic

Ways Pays

An explanation of this mechanic and its rules.

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Game mechanic

Wild Symbols

Wild symbols can substitute for certain symbols to form eligible wins. Their substitution rules differ: some wilds expand, stick to positions, move, or carry multipliers, while others have restricted behavior.How it…

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Game mechanic

Wild Symbols; Free Spins; Bonus Buy; Multipliers

An explanation of this mechanic and its rules.

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Game mechanic

Win Multipliers

A multiplier increases a defined payout component according to the game rules. It might multiply a single line win, a cluster, a feature total, or another amount. Displayed multipliers are not…

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Educational reference only. Feature names and rules can vary between game titles and configurations; always check the publisher’s official game instructions.