This baseball glossary explains the terms, statistics, and slang you will hear at the ballpark or on a broadcast, in plain language. It is organized by topic: game and rules terms, pitching, hitting, fielding and positions, statistics, and common slang. If you are new to baseball, start with the game and rules terms, since they explain how outs, runs, and innings work. If you already know the basics, the statistics section will help you follow modern broadcasts and analysis.
Rulebook note: definitions here are simplified for readability. Official rules differ in detail between MLB, NCAA, NFHS high school baseball, and youth organizations such as Little League. For exact wording, consult the current official rulebook for your level.
Game and rules terms
| Term | Meaning |
|---|---|
| At-bat | A batter’s turn at the plate that ends in a hit, an out, or an error, not counting walks, hit-by-pitches, sacrifices, and certain other outcomes |
| Plate appearance | Any completed turn at the plate, including walks and sacrifices |
| Balk | An illegal motion by the pitcher with runners on base; runners advance one base |
| Infield fly rule | With runners on first and second, or bases loaded, and fewer than two outs, the batter is out on a fair fly ball that an infielder can catch with ordinary effort |
| Force out | An out made by touching a base that a runner is forced to advance to |
| Tag out | An out made by touching a runner with the ball or the glove holding the ball |
| Tag up | A runner returning to touch a base on a caught fly ball before advancing |
| Double play | Two outs recorded on one continuous play |
| Sacrifice | An out made intentionally to advance a runner, by bunt (sacrifice hit) or fly ball (sacrifice fly) |
| Walk (base on balls) | Four pitches outside the strike zone that the batter does not swing at, awarding first base |
| Hit by pitch | A pitch that touches the batter, usually awarding first base |
| Walk-off | A play by the home team that ends the game in the final inning |
| Extra innings | Innings played after the regulation length when the score is tied |
Pitching terms
| Term | Meaning |
|---|---|
| Strike zone | The area over home plate, roughly between the batter’s midsection and knees, through which a pitch counts as a strike |
| Fastball | The fastest pitch in most arsenals, including four-seam and two-seam variations |
| Changeup | An off-speed pitch that looks like a fastball but arrives slower |
| Curveball | A slower breaking pitch that drops with topspin |
| Slider | A breaking pitch thrown harder than a curveball with shorter, mostly sideways break |
| Cutter | A fastball with slight, late sideways movement |
| Splitter | A pitch gripped with spread fingers that drops sharply |
| Windup and stretch | The two basic pitching deliveries; the stretch is used with runners on base |
| Pickoff | A throw from the pitcher or catcher to catch a runner off base |
| Bullpen | The area where relief pitchers warm up, and the team’s group of relievers |
| Pitch count | The number of pitches a pitcher has thrown, often limited for arm health |
Hitting terms
| Term | Meaning |
|---|---|
| Single, double, triple | Hits on which the batter reaches first, second, or third base safely |
| Home run | A hit on which the batter circles all the bases and scores, usually by hitting the ball over the fence |
| Grand slam | A home run with the bases loaded, scoring four runs |
| Bunt | A soft, intentional tap of the ball with a held bat |
| Hit-and-run | A play in which the runner breaks with the pitch and the batter tries to hit the ball on the ground |
| Count | The number of balls and strikes, stated balls first, such as 2-1 |
| Full count | Three balls and two strikes |
| Check swing | A swing the batter tries to stop; umpires decide whether it was a strike |
| Line drive | A hard-hit ball with a low, flat trajectory |
| Pop-up | A high, short fly ball, usually in the infield |
Fielding and positions
| Term | Meaning |
|---|---|
| Battery | The pitcher and catcher together |
| Infield | First base, second base, shortstop, and third base, plus the area they cover |
| Outfield | Left field, center field, and right field |
| Position numbers | Scoring numbers: 1 pitcher, 2 catcher, 3 first base, 4 second base, 5 third base, 6 shortstop, 7 left field, 8 center field, 9 right field |
| Error | A misplay by a fielder that allows a batter or runner to reach or advance when an ordinary effort would have made the out |
| Cutoff | A fielder who intercepts a throw from the outfield to redirect it |
| Shift | Repositioning fielders based on a hitter’s tendencies; restricted at some levels |
| Assist and putout | Scoring credits for fielders who help make or complete an out |
Statistics
| Term | Meaning |
|---|---|
| AVG | Batting average: hits divided by at-bats |
| OBP | On-base percentage: how often a batter reaches base by hit, walk, or hit-by-pitch |
| SLG | Slugging percentage: total bases divided by at-bats |
| OPS | On-base plus slugging: OBP added to SLG |
| RBI | Runs batted in: runs that score because of a batter’s action, with some exceptions |
| ERA | Earned run average: earned runs allowed per nine innings |
| WHIP | Walks plus hits per inning pitched |
| K and BB | Strikeouts and walks |
| WAR | Wins above replacement: an estimate of a player’s total value compared with a replacement-level player; calculations vary by source |
Reading a box score
A box score summarizes a game using many of the terms above. For hitters, columns usually show at-bats (AB), runs (R), hits (H), runs batted in (RBI), walks (BB), and strikeouts (SO or K), often followed by season batting average. For pitchers, the box score lists innings pitched (IP), hits, runs, earned runs (ER), walks, strikeouts, and ERA. Innings pitched are recorded in thirds, so 6.1 means six and one-third innings and 6.2 means six and two-thirds. Once you know these abbreviations, a box score tells the story of a game at a glance.
Common slang
| Term | Meaning |
|---|---|
| Can of corn | An easy fly ball |
| Dinger, tater, bomb | A home run |
| Frozen rope | A hard, straight line drive |
| Texas leaguer | A bloop hit that falls between infielders and outfielders |
| Painting the corners | Pitching precisely at the edges of the strike zone |
| Chin music | A high, inside pitch near the batter’s head |
| Golden sombrero | Striking out four times in one game |
| Cycle | Hitting a single, double, triple, and home run in the same game |
| Ace | A team’s best starting pitcher |
| Rookie | A player in their first season at a given level, according to league criteria |
How to learn baseball terms quickly
- Start with the basics. Learn outs, innings, balls and strikes, and the bases before moving to stats.
- Watch with a scorecard. Keeping score introduces position numbers and scoring symbols naturally.
- Listen to broadcasts. Announcers explain terms in context, which helps them stick.
- Focus on a few stats. AVG, OBP, and ERA are a good starting point before advanced metrics.
- Ask questions. Players, coaches, and fans are usually happy to explain.
Commonly confused terms
- At-bat versus plate appearance. Walks and sacrifices count as plate appearances but not at-bats.
- Earned versus unearned runs. Runs that score because of errors or passed balls may be unearned and do not count toward ERA.
- Force out versus tag out. Force outs only require touching the base; tag outs require tagging the runner.
- Hit versus error. The official scorer decides whether a batter reached on a hit or because of a fielding mistake.
- Balk versus illegal pitch. Related but distinct rules; a balk applies with runners on base.
Frequently asked questions
What is the infield fly rule?
With runners on first and second, or bases loaded, and fewer than two outs, the batter is automatically out on a fair fly ball that an infielder can catch with ordinary effort. It prevents fielders from dropping the ball on purpose to get a double play.
What does OPS mean in baseball?
OPS stands for on-base plus slugging. It adds a player’s on-base percentage and slugging percentage to give a quick measure of overall hitting.
What is a walk-off in baseball?
A walk-off is a play by the home team that scores the winning run in the final inning, immediately ending the game.
