The MLB Betting Glossary: Every Term, Market & Prop Explained
From YRFI and NRFI to F5, run line, RBI props, K props, and event contracts on Kalshi, Polymarket, Robinhood and Coinbase — the complete plain-English glossary for MLB betting and baseball event trading.
Baseball has the densest market menu of any U.S. sport. Between sportsbooks, prediction markets, and DFS-style apps, there are dozens of ways to take a position on a single MLB game. Here's the complete plain-English glossary.
Core game markets
Moneyline (ML) — Straight pick of who wins the game. -140 means risk $140 to win $100; +120 means risk $100 to win $120. Baseball moneylines move all day around starting pitchers.
Run Line (RL) — Baseball's version of a point spread, almost always set at -1.5 / +1.5. The favorite has to win by 2+; the underdog can lose by 1 or win outright. Run line on a heavy favorite (-200 ML) often pays around +120 to +140 because of how often baseball games finish within a run.
Total (Over/Under) — Combined runs by both teams. Most MLB totals sit between 7 and 11 depending on parks, pitchers, and weather. The "juice" (vig) on totals often moves more than the number itself.
Alternate Run Lines — Custom spreads like -2.5, -3.5, +2.5. Heavy favorites at -2.5 pay better but require a real blowout.
Inning-specific markets (where sharps live)
F5 / First 5 Innings — A separate market for the score after 5 innings. Removes bullpen variance and isolates the starting pitcher matchup. Sharps love F5 because it's a cleaner bet on pitching than the full game.
YRFI — Yes Run First Inning — Will at least one run score in the top OR bottom of the 1st? Typically priced -110 to +110 depending on the matchup. Heavily influenced by leadoff hitters and how a starter typically gets through the order the first time.
NRFI — No Run First Inning — The flip side. Will the 1st inning be scoreless? Aces vs weak leadoff trios make this market move.
F3 / F7 — First 3 or first 7 innings totals/sides on some books. Less liquid but useful for ace-vs-ace games.
Player props
Strikeouts (Ks) — Total strikeouts for a pitcher in the game. The most-bet pitcher prop. Moves on opponent strikeout rate, umpire (yes, umpire) and weather.
Hits Allowed / Earned Runs / Outs Recorded — Other pitcher props. "Outs Recorded" (sometimes "Pitcher Outs") is essentially how deep a starter goes — 18 outs = 6 innings.
Total Bases (TB) — Combined bases on a hitter's hits. A single = 1, double = 2, triple = 3, HR = 4. Common lines: 1.5 and 2.5.
Hits + Runs + RBIs (H+R+RBI) — A combined hitter prop. Less volatile than home-run props.
Home Run (HR) Props — Yes/no the player hits a home run, usually +200 to +600. High variance, low hit rate.
RBI Props — Player to record 1+ or 2+ RBIs. Heavily lineup-spot dependent.
Stolen Base / Doubles / Triples — Niche specials, thinner liquidity, occasional sharp action.
Live & alternate markets
Live Lines — In-game moneyline, total, and run line that update pitch-by-pitch. Sharp opportunity when a starter shows command issues early but the line hasn't fully adjusted.
Alternate Totals — Buy/sell the total at non-standard numbers (e.g., over 6.5 instead of over 8.5) for different prices.
Same-Game Parlay (SGP) — Combine multiple markets from one game. Books love these because the implied juice compounds.
Season-long & futures markets
Win Totals — Over/under regular season wins for each team. Posted in February/March and trades all season.
Division Winner — Yes/no a team wins their division (AL East, NL West, etc.).
Playoff Odds — Yes/no a team makes the postseason.
World Series Winner — Outright price on each team to win the WS.
Pennant Winners (AL/NL) — League champion futures.
AL/NL MVP, Cy Young, Rookie of the Year, Manager of the Year — Individual awards.
Home Run Leader, Batting Title, Stolen Base Leader — Stat-leader futures.
Unique MLB event contracts (Kalshi · Polymarket · Robinhood · Coinbase)
100-Win Team This Season — Yes/no any team reaches 100 wins.
Will Any Team Win 110+ Games? — Higher bar; pricing reflects historical rarity (only a handful per decade).
Triple Crown Winner — Yes/no any hitter leads their league in AVG, HR, and RBI. Extremely rare.
No-Hitter This Week / This Month — Polymarket, Kalshi, Robinhood and Coinbase periodically list these as recurring contracts. Sharp flow shows up on big-K pitcher start days.
Perfect Game This Season — Multi-year aggregate, very low yes price.
Will [Player] Hit 50+ HRs? — Single-season milestone contracts on top sluggers.
Will [Pitcher] Win 20+ Games? — Throwback milestone, rarer in modern game.
First No-Hitter / First Player to Hit 30 HR / First Team to 50 Wins — "Race" contracts.
Sharp-money & line-movement terminology
Sharp Money — Wagers from professional, well-informed bettors.
Public Money / Square Money — Wagers from casual, fan-driven bettors.
Steam Move — Multiple books reprice the same MLB line in the same direction within minutes. (See Steam Moves Explained.)
Reverse Line Movement (RLM) — The line moves opposite the direction of public ticket count. (See Reverse Line Movement.)
Handle — Total dollars wagered on a market.
Tickets — Number of individual bets placed (not the dollar amount).
Limits — The max a book will let you wager. Sharps get limited; the public gets full limits.
Closing Line Value (CLV) — Beating the final line before first pitch. The single best long-term indicator that you're a winning MLB bettor.
Juice / Vig — The book's built-in commission. Standard is -110 (you risk $110 to win $100), but moves on alternate markets.
Push — A tie that returns your stake. Common on run lines and totals that land exactly on integer numbers.
Baseball-specific context terms
LHP / RHP — Left-handed / right-handed pitcher.
Bullpen Day / Opener — A team starts a reliever for 1-2 innings before going to a "primary" pitcher.
TTOP — Times Through the Order Penalty — A starter's effectiveness drops the second and especially third time facing the same lineup.
Park Factor — How a stadium affects scoring. Coors Field is the biggest run-booster; Oracle Park is one of the biggest suppressors.
Wind In / Wind Out — Wind direction at outdoor parks. A 15+ mph "out" wind at Wrigley can move a total a full run.
Umpire Factor — Plate umpire strike-zone tendencies. Some umps inflate Ks and suppress runs; others do the opposite.
Travel Spot / Getaway Day — Day game after a night game, or final game of a road trip — historically lower-effort spots.
Bankroll & process terms
Unit — Your standard bet size, usually 1% of bankroll. "I'm down 3 units" means you've lost 3% of your stake.
Bankroll — The total amount of money set aside for betting. Should be money you can afford to lose entirely.
CLV — Closing Line Value — The difference between the price you got and the closing price. Consistent positive CLV is the single best predictor of long-term profitability.
EV — Expected Value — The mathematical edge of a bet over many repetitions. A +EV bet wins money over the long run regardless of any single outcome.
Kelly Criterion — A formula for sizing bets based on your edge. Most pros use "fractional Kelly" (¼ or ½) to reduce variance.
Flat Stake — Betting the same amount on every play. The recommended starting approach for new bettors.
Tilt — Emotional betting after a losing streak. The fastest way to destroy a bankroll.
ROI — Return on Investment — Total profit divided by total amount wagered. A 3% ROI over a full MLB season is excellent.
Yield — Same as ROI but more commonly used in European markets.
Event-contract & prediction-market terms
Yes / No Contract — On Kalshi, Polymarket, Robinhood, and Coinbase, you buy "Yes" or "No" shares of an outcome between $0.01 and $0.99. Each share pays $1 if your side wins.
Implied Probability — The price of a Yes contract converted to a percentage. A Yes share at $0.42 implies a 42% market probability.
Liquidity — How much money is available to trade at the current price. Low-liquidity contracts move on small orders.
Spread (Bid–Ask) — The gap between the best buy and sell price. Tight spreads = efficient market.
Resolution — When an event-contract market settles based on the official outcome (e.g., MLB final standings or World Series winner).
Settlement Source — The official data source used to resolve the market. Always check before trading a futures contract.
How to use this glossary
Use the live MLB signal feed — every market type above gets a Heat score. Filter by market (sides, totals, F5, props, futures) to find where sharps are moving today. Pair this glossary with What Is Sharp Money?, How to Bet on Baseball, and Baseball Betting Strategy to put it all together.
For entertainment purposes only. Not betting advice. Markets carry risk — only stake what you can afford to lose.