Bonus Round
A bonus round is a special feature within a slot or casino game — separate from normal play — that unlocks under set conditions and offers enhanced or alternative ways to win.
Definition
A bonus round is a distinct game state that a player enters when a trigger condition is met, such as landing a required number of scatter symbols. Inside it, the game applies alternative or amplified mechanics — common examples include free spins, pick-and-click prizes, win multipliers, expanding symbols, or a bonus wheel. In game-math terms, a large share of a title's total return to player (RTP) is often concentrated in its bonus round, so trigger frequency and average bonus value are among the most important levers a game mathematician tunes. It is a separate concept from a promotional "bonus" such as a deposit match, even though both share the word.
Worked example
Consider a slot with an overall RTP of 96%, split so that the base game returns about 65% and a free-spins bonus round returns the remaining 31%. The bonus triggers on average once every 180 spins (roughly 0.56% of spins) and awards 10 free spins with a 3x multiplier applied to all wins. Because nearly a third of the game's long-run payout is concentrated in a feature that appears rarely, stretches of play without the bonus can feel flat, while a triggered bonus produces most of the game's larger wins — an illustration of how bonus design shapes volatility, not a suggestion that the feature is due or likely on any given spin.
Why it matters
The bonus round is where much of a game's volatility, standout wins, and RTP concentration live, so it is central to how a title actually plays. For math and design practitioners, tuning trigger frequency against average bonus value is how a target RTP and volatility profile are reached. For operators, product, and marketing staff, it is a key engagement mechanic that must be described accurately — as a game feature, never as a shortcut to guaranteed or easy wins. Learners also benefit from separating the in-game "bonus round" (game math) from a promotional "bonus" (an operator offer), two unrelated ideas that beginners routinely confuse.
Related
Note: The general definition is stable across the industry. Specifics vary: the exact RTP split between base game and bonus, trigger frequency, and mechanics are set per game by the supplier. Directly purchasing entry to a bonus round ("bonus buy" / "feature buy") is restricted or not permitted in some markets — for example, it is not available to players in the Great Britain market — so availability should be verified against the relevant jurisdiction and operator.