What is a roulette glossary for?

A roulette glossary provides clear definitions of the terms used across the game and its variants. It is useful when reading about bet types, wheel structure, or rules and encountering a term that is unfamiliar. Definitions here are structural, not strategic.

What is the difference between inside and outside bets?

Inside bets are placed on individual numbers or small groups within the number grid. They cover fewer pockets and pay at higher ratios (up to 35:1). Outside bets are placed in the zones around the grid, covering broader groupings such as colour, high/low, or a dozen. They pay at lower ratios (1:1 or 2:1) and cover 12 to 18 numbers.

What does En Prison mean in roulette?

En Prison is a rule found in French roulette. When the ball lands on zero, even-money bets (Red/Black, Odd/Even, High/Low) are held for the next spin rather than lost immediately. If the next spin produces a winning result for the held bet, the original stake is returned in full. If not, the stake is lost. En Prison and La Partage are alternative rules.

What is the house edge?

The house edge is the mathematical advantage the casino holds, derived from the gap between true odds and payout ratios. In European roulette, the single zero creates a gap between the 36:1 true odds of hitting a number and the 35:1 payout. It is a fixed structural property, not a result that varies between sessions.

What is an RNG in online roulette?

RNG stands for Random Number Generator. It is the software used in online roulette to determine outcomes in place of a physical wheel. Certified RNGs are independently tested to confirm that results are random and not influenced by previous outcomes or external factors.

Roulette Glossary: Key Terms Explained

How To Use This Glossary

Each section below covers a different area of the game: wheel components, table layout, bet types, French roulette rules, payout concepts, gameplay mechanics, betting systems, and variants. Use the section headings to jump to the category you need. If a term is referenced on another page in the Roulette Hub, such as on the how to play roulette guide, you will find its definition here.

Definitions are intentionally concise and structural. They describe what each term refers to in the context of roulette. They do not recommend bets, suggest approaches, or assess the value of any system or rule.

Roulette Wheel Terms

The roulette wheel is the physical or virtual mechanism that determines outcomes. The terms below relate to its structure and components.

Term	Definition
Wheel	The spinning disc is divided into numbered, coloured pockets where the ball lands to determine the outcome of each round.
Pocket	An individual numbered slot on the wheel. Each pocket is assigned a number and a colour. The ball comes to rest in one pocket per spin.
Single zero (0)	A green pocket found on American, European, and French roulette wheels. It adds one outcome to the wheel beyond the 36 numbered pockets.
Double zero (00)	A second green pocket, present only on American roulette wheels. Its addition increases the total number of pockets to 38.
Fret	The metal dividers between pockets on the wheel. Frets separate each pocket and help determine where the ball settles.
Ball track	The outer rim of the wheel, along which the ball travels before losing speed and dropping into a pocket.
Number sequence	The specific order in which numbers are arranged around the wheel. The sequence is not consecutive; numbers are distributed to alternate between high and low values and between odd and even.
Canoe / deflector	Small obstacles positioned inside the wheel bowl that affect the ball's path as it drops from the track, contributing to the unpredictability of outcomes.

Roulette Table Layout Terms

The roulette table is the betting surface where players place chips before each spin. It is divided into distinct areas, each corresponding to different bet types.

Term	Definition
Layout / Felt	The printed betting surface of the roulette table, showing the number grid and outside bet areas.
Inside area	The numbered section of the table (covering 1 to 36, plus 0 and 00 where applicable). Inside bets are placed directly on individual numbers or small groups of numbers.
Outside area	The section surrounding the main number grid. Outside bets cover larger groups of numbers and are placed in clearly labelled zones such as Red/Black or Odd/Even.
Column	One of three vertical groups of 12 numbers on the betting grid. A column bet covers all 12 numbers in that group.
Dozen	One of three sequential groupings: 1-12, 13-24, or 25-36. A dozen bet covers all 12 numbers in the chosen range.
Racetrack	An oval-shaped betting area found on French roulette tables. It mirrors the physical layout of the wheel and is used to place announced bets.
Neighbours	A bet type covering a specific number and the numbers immediately adjacent to it on the wheel, typically two on each side. Placed using the racetrack.
Chip	The token used to represent a stake at the roulette table. At physical tables, each player typically uses a distinct chip colour to avoid confusion.

See the how to play roulette guide for a walkthrough of how each area of the table functions during a round.

Inside Bet Terms

Inside bets are placed within the numbered grid on the table. They cover fewer numbers per bet and pay at higher ratios than outside bets.

Term	Definition
Straight up	A bet placed on a single number. Covers one pocket. Pays 35:1.
Split	A bet placed on the line between two adjacent numbers on the grid. Covers two pockets. Pays 17:1.
Street	A bet placed on a row of three consecutive numbers. Chips are placed at the end of the row. Pays 11:1.
Trio	A three-number bet that includes zero. Valid combinations in European and French roulette are 0-1-2 and 0-2-3. Pays 11:1.
Corner (square)	A bet placed at the intersection of four numbers on the grid. Covers four pockets. Pays 8:1.
Basket (First Four)	A bet covering 0, 1, 2, and 3. Available in single-zero roulette variants. Pays 6:1.
Top line (First Five)	A bet covering 0, 00, 1, 2, and 3. in American roulette, pays 6:1. A bet covering 0,1,2, and 3 in European roulette, pays 8:1
Six line (Double Street)	A bet covering two adjacent rows of three numbers, totalling six pockets. Pays 5:1.

Outside Bet Terms

Outside bets are placed in the zones around the number grid. They cover 12 to 18 numbers per bet and pay at lower ratios than inside bets. The zero pocket is not covered by any outside bet.

Term	Definition
Red / Black	A bet on whether the winning number will be red or black. Covers 18 numbers. Pays 1:1. Zero is neither red nor black.
Odd / Even	A bet on whether the winning number will be odd or even. Covers 18 numbers. Pays 1:1. Zero is not counted as odd or even.
High / Low (1-18 / 19-36)	A bet on whether the winning number falls in the lower half (1-18) or upper half (19-36) of the number range. Pays 1:1. Zero does not fall in either group.
Dozens	A bet on one of three groups of 12 consecutive numbers: 1-12, 13-24, or 25-36. Pays 2:1.
Columns	A bet on one of three vertical columns of 12 numbers on the table layout. Pays 2:1.
Even-money bet	Any outside bet that pays 1:1. Includes Red/Black, Odd/Even, and High/Low. These are the bets to which La Partage and En Prison rules apply in French roulette.

The zero pocket is not covered by any outside bet. If zero lands, all outside bets lose.

French Roulette Rule Terms

French roulette uses the same single-zero wheel as European roulette but adds specific rules that affect how even-money bets are resolved when zero lands. The terms below are specific to French roulette.

Term	Definition
La Partage	A French roulette rule applied to even-money bets when zero lands. Half the stake is returned to the player. The other half goes to the house. La Partage applies to Red/Black, Odd/Even, and High/Low only.
En Prison	An alternative to La Partage, also applied to even-money bets when zero lands. Instead of returning half the stake, the bet is held (imprisoned) for the next spin. If the next spin wins, the full stake is returned. If it loses, the stake is lost.
Announced bets	Pre-defined combinations of numbers placed using the racetrack area on a French roulette table. They are called out (announced) by the player and cover specific sections of the wheel. The main categories are Voisins du Zero, Tiers du Cylindre, and Orphelins.
Voisins du Zero	An announced bet covering 17 numbers neighbouring zero on the wheel. Requires 9 chips. Specific bets are distributed across splits, corners, and a street.
Tiers du Cylindre	An announced bet covering 12 numbers on the opposite side of the wheel from zero. Requires 6 chips, placed as splits.
Orphelins	An announced bet covering the 8 numbers on the wheel not included in Voisins du Zero or Tiers du Cylindre. Can be placed as straight-up bets (Orphelins en Plein, 8 chips) or splits (Orphelins a Cheval, 5 chips).
Jeu Zero	An announced bet covering the 7 numbers closest to zero on the wheel: 12, 35, 3, 26, 0, 32, and 15. Requires 4 chips.
Finales en Plein	An announced bet covering all numbers ending in the same digit. For example, a Finale 3 covers 3, 13, 23, and 33. Typically requires 3 to 4 chips.
Finales a Cheval	An announced bet covering all numbers ending in one of two digits, placed as splits. Typically requires 4 to 5 chips.
Rien ne va plus	French phrase meaning 'no more bets', announced by the dealer when the betting window closes. No additional bets or changes are permitted after this point.

Payout and Odds Terms

These terms describe how outcomes are measured, how wins are calculated, and the mathematical relationship between the wheel structure and what a winning bet returns.

Term	Definition
Payout / Payout ratio	The amount a winning bet returns relative to the stake, expressed as X:1. A payout of 35:1 means a winning 1-unit stake returns 35 units in profit plus the original stake.
Odds	The probability of a specific outcome occurring, based on the total number of possible results. On a 37-pocket wheel, a single number has a 1 in 37 chance of winning.
True odds	The actual probability of an outcome, calculated from the wheel structure alone, without the effect of the zero pocket. The true odds of hitting one number on a 37-pocket wheel are 36:1.
House edge	The mathematical advantage the house holds over the player, derived from the gap between true odds and payout ratios. The zero pocket is the structural source of this gap. It is a fixed property of the game, not a per-session outcome.
Return to Player (RTP)	The theoretical percentage of total wagered money that a game returns to players over a large number of rounds. RTP is the inverse of house edge and applies to the game as a whole, not to individual sessions.
Bet coverage	The proportion of wheel pockets covered by a given bet. A straight-up bet covers 1 out of 37 pockets. A Red/Black bet covers 18 out of 37.
Independent event	Each spin of the roulette wheel is an independent event. The outcome of one spin has no effect on the outcome of any future spin, regardless of previous results.

Game Mechanics Terms

These terms cover the operational aspects of a roulette round, whether played at a physical table or in an online environment.

Term	Definition
Croupier / Dealer	The casino staff member who runs the roulette table. The croupier accepts bets, spins the wheel, announces the result, clears losing bets, and pays winning ones.
Marker / Dolly	A small token placed on the winning number on the table layout after each spin. The marker remains in place while the table is settled. No bets may be placed or removed while the marker is down.
Betting window	The period in each round during which players may place, adjust, or remove bets. The window opens at the start of each round and closes before or shortly after the wheel is spun.
RNG (Random Number Generator)	Software used in online roulette to determine outcomes. The RNG replicates the randomness of a physical wheel. Certified RNGs are independently audited for fairness.
Live dealer roulette	An online format where a human croupier operates a real wheel in a studio, streamed in real time to players. Bets are placed through the on-screen interface. Live dealer roulette requires a real-money account.
Spin	One complete round of roulette: from the opening of the betting window through the release of the ball to the settlement of all bets.
Session	A player's continuous period of play, from the first bet placed to the last.
Table limit	The minimum and maximum bet amounts permitted at a given table. Minimums and maximums may differ for inside and outside bets.
Bankroll	The total funds a player has set aside for wagering. Managing bankroll means deciding in advance how much to spend in a session.

Betting system terms

Betting systems are structured methods for sizing or sequencing bets across multiple rounds. They do not change the outcome of any spin, alter the house edge, or affect the probability of any result. The terms below define the main concepts.

Term	Definition
Betting system	A structured approach to determining how much to stake in each round, based on a defined rule. Systems do not affect wheel outcomes or alter probabilities.
Positive progression	A betting system in which the stake increases after a win. The Paroli and Reverse Martingale are positive progression systems.
Negative progression	A betting system in which the stake increases after a loss. The Martingale, Fibonacci, and D'Alembert are negative progression systems.
Base stake / Unit	The fixed starting amount used as the reference point within a betting system. All stake adjustments are calculated as multiples or additions of the base stake.
Martingale	A negative progression system in which the stake is doubled after each loss and returned to the base stake after a win.
Grand Martingale	A variation of the Martingale. The stake is doubled after a loss, plus one additional unit is added. Stakes escalate more rapidly than the standard Martingale.
D'Alembert	A system in which the stake increases by one unit after a loss and decreases by one unit after a win.
Fibonacci	A negative progression system in which stakes follow the Fibonacci number sequence (1, 1, 2, 3, 5, 8, 13...) after losses.
Labouchere	A system using a number sequence. The stake for each round equals the sum of the first and last numbers in the sequence. Numbers are crossed out after wins and added after losses.
Paroli	A positive progression system in which the stake increases after a win, up to a fixed number of consecutive wins (typically three), then resets to the base stake.

For a full mechanical breakdown of each system, see our roulette betting systems guide.

Roulette Variant Terms

Roulette is available in several distinct versions, each with structural differences that affect the wheel, the table, and specific rules.

Term	Definition
European roulette	A variant using a single-zero wheel with 37 pockets (0 to 36). The most widely available form of the game online.
American roulette	A variant using a double-zero wheel with 38 pockets (0, 00, and 1 to 36). The additional zero pocket changes the structure of odds and payouts.
French roulette	A variant sharing the European wheel structure but incorporating La Partage or En Prison rules for even-money bets, and a racetrack for announced bets.
Mini roulette	A compact variant typically using a 13-pocket wheel (0 to 12). Bet types are simplified to reflect the smaller wheel.
Speed roulette	A live dealer variant with reduced time between spins. The game mechanics are otherwise identical to standard roulette.
Auto roulette	A live-streamed roulette format in which the wheel is operated mechanically, without a human dealer present.
Multiwheel roulette	A format in which players can bet on multiple wheels simultaneously within a single round.

For a side-by-side comparison of the main variants, see our roulette variants guide.

What is a roulette glossary for?
A roulette glossary provides clear definitions of the terms used across the game and its variants. It is useful when reading about bet types, wheel structure, or rules and encountering a term that is unfamiliar. Definitions here are structural, not strategic.
What is the difference between inside and outside bets?
Inside bets are placed on individual numbers or small groups within the number grid. They cover fewer pockets and pay at higher ratios (up to 35:1). Outside bets are placed in the zones around the grid, covering broader groupings such as colour, high/low, or a dozen. They pay at lower ratios (1:1 or 2:1) and cover 12 to 18 numbers.
What does En Prison mean in roulette?
En Prison is a rule found in French roulette. When the ball lands on zero, even-money bets (Red/Black, Odd/Even, High/Low) are held for the next spin rather than lost immediately. If the next spin produces a winning result for the held bet, the original stake is returned in full. If not, the stake is lost. En Prison and La Partage are alternative rules.
What is the house edge?
The house edge is the mathematical advantage the casino holds, derived from the gap between true odds and payout ratios. In European roulette, the single zero creates a gap between the 36:1 true odds of hitting a number and the 35:1 payout. It is a fixed structural property, not a result that varies between sessions.
What is an RNG in online roulette?
RNG stands for Random Number Generator. It is the software used in online roulette to determine outcomes in place of a physical wheel. Certified RNGs are independently tested to confirm that results are random and not influenced by previous outcomes or external factors.

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