Action
Money wagered on a market. Books talk about 'taking action' or 'balanced action.' In MLB, also a bet type that stands regardless of starting-pitcher changes (as opposed to 'Listed,' which voids on a starter scratch).
// LEARN · GLOSSARY
// REFERENCE
THE LANGUAGE
OF THE MARKET.
Every term used across the Learn section, defined in one paragraph. Each entry links back to the canonical article where the concept is explored at full depth.
A
Alternate line
A spread or total at a different number than the main line, with a corresponding price adjustment. Buying favoritism (a smaller spread) costs juice; selling favoritism (a larger spread) gains it.
American odds
The default US odds format. Negative numbers indicate favorites (you risk that amount to win 100). Positive numbers indicate underdogs (you risk 100 to win that amount). -110 means risk 110 to win 100.
Arbitrage
Betting both sides of a market across different books at prices that sum to less than 100% implied probability, locking in a guaranteed return regardless of outcome. Hard to execute consistently at retail.
Asian handicap
A two-way soccer market that handicaps one side by half-goal or full-goal increments to remove the draw from the equation. Cleaner pricing and lower hold than the three-way moneyline; the workhorse market for sharp soccer bettors.
B
Bankroll
The amount of money you have allocated to betting that you can afford to lose without affecting your life. Not your sportsbook balance; the dedicated separation between betting and the rest of your finances.
Back-to-back (B2B)
A team playing on consecutive nights. Common in the NBA and NHL. Typically associated with reduced performance for the second-game team; books price the fatigue effect at 1.5 to 3.5 points depending on configuration.
Bowl game
Postseason college football game. Markets are structurally different from the regular season because of opt-outs, coaching transitions, and the schedule gap between the regular season and the bowl.
Both teams to score (BTTS)
Soccer prop market on whether both teams will score at least one goal. Often priced near -110/-110; pricing shifts toward yes or no in matchups with strong attack or strong defense.
C
CLV (closing line value)
The difference between the price you bet and the closing line of the same market. Positive CLV is the cleanest evidence available to a retail bettor that they are betting at +EV prices.
Cover
A favorite covers when it wins by more than the spread. An underdog covers when it stays within the spread or wins outright. Pushing (the result lands exactly on the spread) is neither covering nor failing to cover.
D
Decimal odds
Odds expressed as a multiplier on stake including the stake. Decimal 2.10 means $1 returns $2.10 if the bet wins. Implied probability is simply 1 / decimal.
Draw (soccer)
A soccer match that ends with the two teams tied after regulation. Priced as a primary outcome on the three-way moneyline; removed from Asian handicap markets through handicap structures.
E
EV (expected value)
The probability-weighted average outcome of a bet. Positive EV means the bet has positive expected long-run profit. Negative EV means the bet has expected long-run loss.
Empty-net goal
An NHL goal scored when the trailing team has pulled the goalie for an extra attacker. Accounts for ~8-10% of all NHL goals. Reshapes both totals and puck-line distributions in the late game.
Expected goals (xG)
The probability-weighted expected goals from each shot taken in a soccer match. The foundational metric for modern soccer analytics; aggregates across the match to a single expected-goals number for each team.
F
F5 (first five innings)
MLB market that settles based on the score after five innings, isolating the starting pitcher's contribution from the bullpen's. Higher juice than full-game markets but useful when the bettor's edge is on the starter.
Fractional odds
The traditional UK format. Express profit as a fraction of stake. 5/2 means a $2 stake returns $5 in profit. Less common in US sportsbooks.
G
GSAx (goals saved above expected)
An NHL goaltending metric. The difference between the goalie's actual saves and the saves an average goalie would make against the same shot quality. Better than save percentage as a measure of goaltender quality.
GEM
A confidence band in WagerBird's confidence model. 96+ confidence on the 25 to 100 scale. The rarest tier the model publishes.
H
Handle
The total amount of money wagered through a sportsbook over a period. ROI is sometimes called 'return on handle' to distinguish it from return on the bettor's bankroll.
Hold
The fraction of total wagers a sportsbook keeps as margin on a balanced market. On a -110 / -110 two-sided market, hold is approximately 4.5%. Hold compounds with parlay legs.
I
Inactives (NFL)
The list of players the team has declared will not play in a given game. Filed 90 minutes before kickoff. Produces some of the largest line moves of the week in the NFL.
Implied probability
The probability of an outcome derived from the odds. For decimal odds, it is simply 1 / decimal. The two sides of a market sum to more than 100%; the excess is the book's hold.
Information cascade
The stable order in which information moves through the sportsbook market: from the event to sharp books, to sharp consensus, to retail books, to public action, to closing line. Sharp groups operate at the front of the cascade; retail bettors live near the back.
J
Juice
The book's margin on a market, also called vig or hold. -110 lines carry 4.5% hold on balanced action.
K
Kelly criterion
The mathematically optimal fraction of bankroll to bet given the edge on a bet. Most professionals use a fractional Kelly (often quarter-Kelly) to dampen drawdowns.
Key numbers
The margins of victory that occur disproportionately often. In NFL, 3 and 7 are dominant. The half-point that crosses a key number is the most leverage-heavy decision in spread betting.
L
Live betting
Betting on a market that the book reprices throughout the event. Higher juice and lower limits than pre-game; book pricing engines run with latency that is the source of edge for fast bettors.
Limit
The maximum bet size a sportsbook will accept on a given market. Sharp books carry high limits; retail books impose customer-specific limits, often lowered after the bettor consistently beats the close.
Listed (MLB)
MLB bet type that voids if either announced starting pitcher does not start. Default for most books. Always preferred over 'Action' in MLB because late starter scratches materially shift the line.
Live betting
In-game betting on a market that the book reprices throughout the event. Higher juice and lower limits than pre-game; book pricing engines run with latency that is the source of edge for fast bettors.
M
Middling
Betting two sides of a market at different lines, hoping the result lands in the gap. Most attractive when the gap crosses a key number. Costs juice on each side; pays full when it middles.
Moneyline
A bet on which side wins outright, no spread. Simplest market on the board. Cleanest pricing in MLB; less efficient on heavy favorites in football and basketball.
Market maker
A sportsbook business model in which the book takes professional action at higher limits and lower hold (~2% on majors), uses informed flow as price discovery, and welcomes winning customers. Pinnacle, BetCRIS, and Circa are the canonical examples.
N
No-vig probability
The implied probability of a market after the book's hold has been mathematically removed. The cleaner read on what the market actually thinks. Sometimes called fair probability or true probability.
P
Pace (basketball)
Possessions per game. The foundational input on basketball totals. NBA pace ranges from ~96 to ~104; college basketball pace ranges from ~60 to ~78. Wider pace variance in college produces wider total distributions.
Pitcher scratch
An MLB starting pitcher pulled from a scheduled start within hours of game time. Bets placed on 'Listed' games are voided when the listed pitcher is scratched; 'Action' bets stand. Always bet 'Listed' unless you have a specific reason not to.
Power play (hockey)
An NHL situation where one team has more skaters on the ice than the other due to a penalty. Power-play efficiency (PP%) and penalty-kill efficiency (PK%) are standard team metrics.
Puck line
The NHL analog to a spread, fixed at -1.5/+1.5. The favorite must win by 2 or more goals. Pricing varies sharply with team strength; the empty-net dynamic reshapes the result distribution in ways unique to hockey.
Parlay
A single ticket combining multiple legs. Every leg must win. Hold compounds: a three-leg parlay of -110 legs runs about 13% hold. Most parlays are negative EV by design.
Prop
A market on a specific within-game outcome (player stat lines, team-level events). Higher juice than sides and totals; higher pricing dispersion makes them a sharp opportunity with a working model.
Push
When the result lands exactly on a spread or total. The bet is refunded. Half-point lines (3.5 instead of 3) eliminate pushes, hence their value around key numbers.
Public bias
Documented systematic preferences of recreational bettors. The seven dominant patterns: favorite, over, primetime, home favorite, recency, brand or franchise, and same-game parlay complexity. Books shade lines into these biases.
R
Rotation (NBA)
The pattern of player substitutions a coach uses through a game. Playoff rotations tighten to 7-9 players; regular-season rotations use 9-10. Affects star prop totals and bench prop totals meaningfully.
Restriction
A sportsbook lowering the maximum bet size on a customer's account, typically because the customer has demonstrated +CLV pattern. The book may also slow-grade bets or eventually close the account.
Reverse line movement (RLM)
When a line moves opposite the direction of public money. A signal that sharp money is on the side the public is fading. One of the few retail-visible sharp signals.
ROI
Return on investment, or more precisely return on handle: total profit divided by total amount staked. The right metric for evaluating long-run strategy quality. Hit rate alone is insufficient.
Run line
The MLB analog to a spread, fixed at -1.5 / +1.5. The favorite must win by 2 or more; the underdog wins outright or loses by 1. Pricing varies across the moneyline range.
Retail book
A sportsbook business model in which the book acquires recreational customers at heavy marketing cost, runs 4 to 5% hold on majors, and limits or restricts winning customers to protect the customer-acquisition economics. FanDuel, DraftKings, BetMGM, Caesars, Fanatics.
S
Series state (NBA)
The current standing of a playoff series (e.g., 2-2, 3-1) and the resulting motivation and tactical context. Single most important input distinguishing playoff modeling from regular-season modeling.
Sharp money
Bets placed by professional or semi-professional bettors with track records of beating the market. Books treat sharp money as informationally meaningful and reprice in response. Square money does not move the line.
Same-game parlay (SGP)
A parlay combining multiple legs from the same game. Pricing accounts for correlation in the book's favor; hold often runs 15 to 35%.
Spread
A handicap applied to the final score. The favorite gives points; the underdog gets points. Standard pricing is -110 / -110. The dominant market in NFL and NBA.
Square money
Bets placed by recreational bettors. Books treat square money as informationally light. Square bias toward favorites, overs, and primetime games shows up as predictable line markups on those sides.
Shading
Moving a line away from the book's true probability estimate to extract additional margin from the side that public bettors prefer. The structural mechanism by which books price into documented public bias.
Steam
A rapid line move across multiple books at the same time, indicating coordinated sharp action. By the time a steam move shows up at a retail book, the value is usually compressed.
T
Three-way moneyline
A soccer betting market with three priced outcomes: home win, draw, away win. Each is priced separately; the implied probabilities sum to >100% reflecting the book's hold.
Trap line
A sportsbook price engineered to attract specific public action that the book wants to take. Common signatures: retail line one to two points off sharp consensus, asymmetric juice on the popular side, falling limits on the unpopular side, marketing emphasis on the popular side. The trap is in the gap between the public's narrative and the sharp model's price.
Tilt
Emotional bet sizing: betting larger after losses to recover, betting larger on 'sure things' that feel more confident than the math justifies, chasing the day's losses with end-of-card prop bets. The single largest cognitive failure in retail betting.
Teaser
A multi-leg ticket where each spread or total moves a fixed number of points in the bettor's favor at reduced odds. Mostly bad bets except for specific 6-point NFL teasers crossing key numbers (Wong teasers).
Total
A bet on the combined score of both teams relative to the book's posted number. Over or under. Often the second-most-bet market behind sides.
U
Unit
A standard bet size, typically 1% to 3% of bankroll. 'Up 5 units' means net profit equal to five times the standard unit size. Without the unit definition, the metric is uninterpretable.
V
Vig (vigorish)
Synonym for juice or hold. The book's margin on a market.
Glossary entries are summary definitions. Treatment in the canonical article is more rigorous. Bet responsibly. 21+ where legal. 1-800-GAMBLER.