Glossary

The standard US odds format, shown as a number with a sign. A favorite is negative (−150 means you risk $150 to win $100); an underdog is positive (+130 means you risk $100 to win $130). See also Decimal odds, Implied probability.

The odds format common outside the US, shown as a single number that is your total return per $1 staked (stake included). 2.50 means a $10 bet returns $25 total — your $10 back plus $15 profit. Even money is 2.00; the same price in American odds is +100.

The traditional UK format, shown as a fraction of profit to stake. 5/2 means you win $5 profit for every $2 staked (a $20 bet returns $70 total). 1/1 is even money, the same as 2.00 in Decimal odds or +100 in American odds.

The win probability a price implies, ignoring the book's cut. For +130, implied probability = 100 / (130 + 100) = 43.5%. Summing both sides' implied probabilities reveals the Vig (juice).

The book's built-in commission, baked into the prices on both sides of a market. If both sides are priced −110, each implies 52.4% and they sum to 104.8% — that extra 4.8% is the vig. Strip it out to get a fair Devig / no-vig price.

The book's expected profit margin on a market, expressed as a percentage of total money wagered. It comes from the Vig (juice): a market where both sides sum to 104.8% has a hold of roughly 4.6% (= 4.8 / 104.8). A lower hold means a better price for bettors.

The number a book posts for a market — a spread, a total, or a price. "The line moved" means that number changed, often in response to bets or news. See Point spread and Total (over/under).

The cost of a bet, expressed in odds. Two bets can share the same Line (say, a −3 spread) but differ in price (−110 versus −105); the better price pays more for the same outcome.

The side more likely to win, priced so it pays less than it costs. A −150 favorite means you risk $150 to win $100. The opposite is the Underdog.

The side less likely to win, priced so it pays more than it costs. A +200 underdog means a $100 bet wins $200 in profit. The opposite is the Favorite.

A price where you risk $1 to win $1 — +100 in American odds, 2.00 in Decimal odds, or 1/1 in Fractional odds. Its implied probability is exactly 50% before vig.

The final price on a market right before it closes (kickoff, tip-off, first pitch). It reflects all the money and information that came in, so it is widely treated as the sharpest estimate of true probability. Beating it is measured by Closing line value (CLV).

How your bet's price compares to the Closing line. If you bet a team at +150 and it closes at +120, you got positive CLV — you locked in a better price than the market settled on. Consistent positive CLV is a strong sign of long-term Edge.

A market price with the book's Vig (juice) removed, giving a fair estimate of true probability. If two sides imply 55% and 50% (summing to 105%), dividing each by 1.05 gives no-vig probabilities of 52.4% and 47.6%. This is the baseline you compare your own estimate against to find Edge.

A bet on who wins outright, no points involved. Priced in American odds: favorites cost more than they pay, underdogs pay more than they cost.

A bet on the margin of victory rather than just the winner. If a team is −6.5, they must win by 7 or more to cover; their opponent at +6.5 covers by winning or losing by 6 or fewer. The half-point removes the chance of a Push.

A bet on the combined score of both teams versus a number the book posts. If the total is 47.5, the over wins on 48+ combined points and the under wins on 47 or fewer. It does not matter who wins the game.

The baseball ("run line") and hockey ("puck line") version of a Point spread, almost always set at 1.5. The favorite at −1.5 must win by 2+; the underdog at +1.5 covers by winning or losing by exactly 1.

A single bet combining multiple selections; all must win to pay out. Odds multiply, so payouts are large — but so is the combined Vig (juice).

A Parlay where you move each Point spread or Total (over/under) in your favor by a set number of points in exchange for a lower payout. A 6-point, two-team football teaser might turn −7.5 and −8 into −1.5 and −2. All legs still must win.

A bet on something other than the final result — often a player or team stat. Examples: a quarterback over 249.5 passing yards, or whether a game's first score is a touchdown.

A bet on an outcome decided far in the future, like a team to win the championship or a player to win MVP. Placed weeks or months out, these Moneyline-style bets often carry high Hold because the book holds your stake for a long time.

A bet placed after the event has started, with prices that update in real time as the game unfolds. A team that falls behind early will get longer odds; the Line shifts constantly until the market is taken Off the board for key moments.

A way to place many small Parlays from a list of selections at once. Pick 4 teams "by 2s" and the book builds all 6 possible two-team parlays, so a single miss does not wipe out everything.

Betting the other side of a position you already hold to lock in profit or cut losses. If your Futures ticket needs one more win, you might bet the opponent so you come out ahead either way. Compare with a Middle.

Betting both sides of a market at different numbers so a result landing in between wins both. Bet over 44.5 early, then under 47.5 after the line moves, and a final total of 45, 46, or 47 cashes both tickets. Even when it misses you only lose the Vig (juice).

The first Line a book posts for a market. Openers often have lower Limits because the book is still learning where the true number sits; they move quickly as the first bets come in.

Any change to a posted Line or Price after it opens. Movement is driven by money coming in on one side, by news (injuries, weather, lineups), or by a book matching its competitors.

A fast, widespread move where a Line shifts across many books at once, usually triggered by a wave of Sharp money. Chasing steam means trying to bet the old number before your book catches up.

Bets from winning, professional bettors whom books respect. When sharp money hits a side, books move the Line quickly even on modest stakes because the information matters more than the amount.

Bets from casual, recreational bettors — "squares." It tends to pile on favorites, overs, and popular teams, which is why a line can move opposite to where the public is betting when Sharp money takes the other side.

The most a book will accept on a single bet or market. Limits start low on the Opening line and rise as the market sharpens; a book may cut a winning customer's limits or take the market Off the board.

The operator that sets prices, takes bets, and pays out winners — a sportsbook. Its profit comes from the Vig (juice) and from balancing action across both sides.

A book (or sharp group) that sets prices first and accepts high Limits, letting the betting tell it where the true number is. Other books copy these prices, so the market maker effectively leads Line movement. Contrast with retail books that mostly follow.

A tie against the number, where the bet is refunded with no win or loss. A −3 favorite that wins by exactly 3 pushes, as does an over 44 on a game totaling exactly 44. Half-point lines ("hooks") like −3.5 or 44.5 exist to avoid pushes.

When a book temporarily stops taking bets on a market, shown as "OTB" or with no price. It usually happens around major news — an injury report or a Live (in-play) bet pause — until the book sets a new Line.

A promotion offering a better Price than standard, such as −105 instead of the usual −110. Lower juice means lower Hold for the book and better long-term value for the bettor.

Betting all outcomes of a market across different books whose prices disagree enough to guarantee a profit no matter the result. If one book has a team at +110 and another has the opponent at +110, staking both correctly locks in a win. Opportunities are small, brief, and limited by each book's Limits.

A standard bet size, used so wins and losses can be compared regardless of Bankroll size. A unit is typically 1% of bankroll, so a $5,000 bankroll means a 1-unit bet is $50. "Up 8 units" means a net profit of 8 times that base bet.

The total money set aside specifically for betting, separate from everyday finances. Its size sets your Unit, and protecting it is the goal behind every Staking plan.

The set of rules for how much to bet on each play. Plans range from Flat betting (same size every time) to scaling by confidence, as in the Kelly criterion.

A Staking plan where every bet is the same size — usually 1 Unit. It is simple, controls Variance, and avoids chasing losses with bigger bets.

The average profit or loss a bet would make if repeated many times. Bet $100 at +150 with a true 45% win chance: EV = 0.45 × $150 − 0.55 × $100 = +$12.50 per bet. Positive EV is the foundation of every winning strategy and comes from having an Edge.

The natural swings in results around your Expected value (EV). Even a profitable bettor can lose for weeks; variance is why a real Edge only shows up over a large sample.

How much better your estimate of an outcome is than the book's price. If you think a team should be +120 (45.5%) and the book offers +150 (40%), your edge is that 5.5-point probability gap. Edge is what makes Expected value (EV) positive and shows up over time as Closing line value (CLV).

A formula for bet sizing that scales your stake to your Edge and the odds, maximizing long-term bankroll growth. It can prescribe large bets, so many bettors use "fractional Kelly" (a half or quarter of the amount) to tame Variance and lower Risk of ruin.

The probability of losing your entire Bankroll before your Edge plays out. Betting too large a Unit raises it sharply; flat, conservative staking keeps it near zero.

Return on investment — net profit divided by the total amount wagered, as a percentage. Win $300 across $10,000 of total bets and your ROI is 3%. In betting, ROI and Yield usually mean the same thing.

Profit as a percentage of total stakes — the same idea as ROI, and the common term in sports betting. A 5% yield over a large sample of bets is considered very strong.