Betting glossary: the key terms explained

Odds and prices

Odds tell you two things: how likely the bookmaker thinks an outcome is, and how much you win if it happens.

• Fractional odds: the traditional UK format, such as 5/1. You win £5 for every £1 staked, plus your stake back
• Decimal odds: the total return per £1, including your stake. 5/1 is 6.0 in decimal, so a £10 bet returns £60
• Evens: odds of 1/1 or 2.0. A £10 winning bet returns £20, which is £10 profit plus your stake
• Odds on / odds against: odds on means your profit is less than your stake; odds against means it is more
• Favourite: the selection with the shortest odds, so the one the bookmaker rates most likely to win
• Implied probability: the chance of an outcome hidden in the odds. Decimal odds of 2.0 imply 50%; 4.0 implies 25%
• Overround (margin): the bookmaker’s built-in profit. Add up the implied probabilities in a market and anything over 100% is the margin
• Price boost: a promotion that lengthens the odds on a selection for a short time, usually with a lower maximum stake

Value betting terms in our betting glossary

This part of our betting glossary covers the terms you will meet most in our value betting guide, which explains how to judge a price rather than pick a winner.

• Value bet: A value bet is one where the odds are higher than the real chance of the outcome suggests. It won’t always win, but over many similar bets the price is in your favour. Our value betting guide explains how to spot one.
• Expected value (EV): Expected value is the average result per £1 staked if you placed a bet many times. You work it out as your probability × decimal odds − 1, so 50% at odds of 2.20 gives +0.10, or 10p per £1. See our guide to expected value betting.
• Fair odds: Fair odds are the odds with the bookmaker’s margin taken out, so the implied chances add up to exactly 100%. They give you a benchmark to compare real prices against. Learn how to work them out in our fair odds guide.
• Sharp bookmaker: A sharp bookmaker takes large bets, runs low margins and moves its prices quickly when informed money arrives. Its prices are often used as the best estimate of the true chance. In the UK, Betfair Exchange prices are the usual benchmark, as our guide to sharp bookmakers explains.
• Soft bookmaker: A soft bookmaker builds wider margins into its odds and is slower to move its prices. That means its odds can sometimes be higher than a sharp market’s fair price. Comparing prices across firms is covered in our odds shopping guide.
• Closing line value (CLV): Closing line value compares the odds you took with the odds just before the event started. CLV % = odds taken ÷ closing odds − 1, so taking 2.10 when it closes at 2.00 is +5%. Read more in our guide to closing line value.

Staking, results and accounts

The rest of this betting glossary section covers how much to stake, how to measure results and what bookmakers can do with your account.

• Kelly criterion: The Kelly criterion is a formula that sets your stake as a share of your bankroll, based on your edge and the odds. Full Kelly is very aggressive, so many people use a fraction of it, such as a quarter. Our Kelly criterion guide shows the maths.
• Staking plan: A staking plan is a set rule for how much you bet each time, such as a flat £5 or 1% of your bankroll. It stops you betting more after wins or chasing losses. See our guide to bankroll management.
• Yield: Yield is your profit divided by the total amount you have staked. For example, £30 profit from £1,000 of bets is a 3% yield. Our guide to betting records explains how yield differs from ROI.
• Variance: Variance is the natural swing in results caused by luck, so short-term results say very little. Our betting variance guide shows how big those swings can be.
• Arbitrage: Arbitrage means backing every outcome of an event at different bookmakers, at prices that should return a profit whatever happens. In practice, prices move, bets can be voided and accounts are often restricted, so it still carries risk. Compare it with other approaches in our guide to value betting vs matched betting.
• Account restrictions: Account restrictions are limits a bookmaker places on a customer, such as cutting maximum stakes or closing the account. UK bookmakers are legally allowed to do this for commercial reasons. Our guide to betting account restrictions covers what to expect.

Bet types

• Single: a bet on one selection
• Accumulator (acca): one bet on several selections that must all win. The odds multiply together, so the return is bigger but the risk is too
• Double, treble: an accumulator with two or three selections
• Bet builder: several selections from the same match combined into one bet, such as a team to win and a player to score
• Each way: two equal bets, one to win and one to place, so £5 each way costs £10
• Lucky 15: four selections combined into 15 bets: four singles, six doubles, four trebles and one four-fold
• Handicap: a virtual head start given to the weaker side, to even up a one-sided match
• Over / under: a bet on whether a total, such as goals or points, will be above or below a set line
• Both teams to score (BTTS): a bet that each side scores at least once
• Outright / ante-post: a bet on the overall winner of a competition, or a race placed well before the day. Ante-post stakes are usually not returned if your selection does not run

Horse racing terms

• Starting price (SP): the official odds when a race starts
• Best odds guaranteed (BOG): if you take a price and the SP is bigger, you are paid at the bigger odds
• Place terms: how many places an each-way bet pays on, and at what fraction of the win odds, such as 1/5 odds for the first four
• Extra places: a promotion that pays each-way bets on more places than usual
• Non-runner: a horse withdrawn before the race. Single bets on it are normally refunded
• Non-runner no bet (NRNB): an ante-post concession that refunds your stake if your horse does not run
• Rule 4 deduction: a cut to winnings when a horse is withdrawn late, because the rest of the field had a better chance than the odds suggested
• Dead heat: two or more runners finishing level. Your stake is split and paid at full odds on each part

Sign-up offers and free bets

The terms that decide what a welcome offer is really worth. Compare live offers.

• Free bet (stake not returned): a bet the bookmaker funds, where you keep the winnings but not the stake
• Qualifying bet: the real-money bet you place to unlock a sign-up offer
• Minimum odds: the shortest odds your qualifying bet can be placed at, often 1/2 (1.5) or evens (2.0)
• Bet credits: bet365’s name for free bet funds. They can be used to bet but not withdrawn
• Expiry: how long you have to use a free bet, often seven days
• Opt-in: some offers only count if you tick a box or use a code at sign-up
• Payment method exclusions: deposits by e-wallets such as PayPal or Skrill sometimes do not qualify for a welcome offer
• Mixed-product promotion: an offer that makes you use more than one product, such as a sports bet unlocking casino spins. Banned in Great Britain since 19 January 2026. Read more
• Matched betting: backing an outcome with a bookmaker and laying it on a betting exchange to lock in the value of a free bet

In-play and settlement

• In-play: betting on an event after it has started
• Cash out: settling a bet early for the amount the bookmaker offers
• Partial cash out: cashing out part of a bet and leaving the rest running
• Void bet: a bet cancelled by the bookmaker, with the stake returned. A void leg in an acca usually stays in at odds of 1.0
• Push: a result exactly on the line, such as a 1-goal Asian handicap won by one goal. Your stake is returned
• Palpable error: a clear pricing mistake. Bookmaker terms let them settle the bet at the correct odds

Casino terms

For a casino offer, these terms decide how much you are likely to keep.

• Wagering requirement: how many times bonus funds or winnings must be played through before withdrawal. Capped at 10x at UK-licensed casinos since 19 January 2026
• No wagering: winnings are paid as withdrawable cash
• Game weighting: how much each game counts towards wagering. Slots usually count 100%, while blackjack and roulette often count less or not at all
• Free spins: spins on a slot at a fixed stake, paid for by the casino
• RTP: the share of stakes a game returns over time. A 96% RTP slot pays back £96 per £100 staked on average
• House edge: the casino’s built-in advantage, equal to 100% minus RTP
• Volatility: how much a slot’s results swing. High volatility means bigger but rarer wins
• Max win cap: the most you can win from a bonus or free spins
• Max bet rule: the largest stake allowed while you play with bonus funds
• Slot stake limit: the most you can stake on one online slot spin in Great Britain: £5, or £2 for players aged 18 to 24
• Live casino: table games such as blackjack and roulette streamed with a real dealer

Safer gambling tools

Every UK-licensed site must offer these. They are free and you can set them up in your account.

• Deposit limit: a cap on how much you can pay in each day, week or month
• Reality check: a pop-up that reminds you how long you have been playing
• Time-out: a short break from a site, from 24 hours up to six weeks
• Self-exclusion: closing your account for at least six months
• GamStop: a free scheme that self-excludes you from every UK-licensed gambling site at once
• Affordability check: a check by the site that you can afford the amount you are spending