Run
A point scored when a runner reaches home plate after touching each base in order.
Basics
The core terms that make the rest of the rules easier to read.
Out
The defence needs 3 outs to end the half-inning.
Inning
Each inning has a top half and bottom half, with both teams batting once.
Hit
A batter reaches base safely by putting the ball in play.
Walk
A batter reaches first base after the pitcher throws four balls outside the strike zone.
Home run
A hit that lets the batter circle all bases and score, usually by leaving the field of play.
Ball
A pitch outside the strike zone that the batter does not swing at.
Strike
A pitch in the strike zone, a swing and miss, or many foul balls.
Batter's box
The marked area beside home plate where the batter stands.
Pitcher's mound
The raised circle where the pitcher starts each pitch.
Flow
How possession, scoring, and switches of play happen.
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1
Pitch from the mound
The pitcher throws from the mound toward home plate.
2
Batter in the box
The batter stands in the batter's box beside home plate.
3
Balls and strikes
Four balls make a walk. Three strikes make a strikeout.
4
Ball in play
If the batter hits a fair ball, they run toward first base while fielders try to get an out.
5
Ways to get out
Common outs include strikeouts, caught fly balls, force outs, and tags.
6
Advance and score
Runners move around the bases and score by reaching home plate.
7
Three outs switch sides
After 3 outs, the batting team takes the field and the other team bats.
Timeline
How long the game runs, and what can change the ending.
Nine innings
Most MLB games are scheduled for 9 innings.
Top and bottom
The away team bats in the top half, and the home team bats in the bottom half.
No bottom 9th if already ahead
If the home team leads after the away team finishes the top of the 9th, the bottom half is not played.
Extra innings
If the game is tied after 9 innings, extra innings are played until one team finishes ahead.
Stats
Plain-English meanings for common challenge columns.
At bats expand_more
At bats
Official batting chances, excluding walks and some other outcomes.
Runs expand_more
Runs
Total team score.
Hits expand_more
Hits
Safe reaches on balls put in play.
RBI expand_more
RBI
Runs batted in, credited to the batter who drives a run home.
Walks expand_more
Walks
Free passes to first base after four balls.
Strikeouts expand_more
Strikeouts
Batters retired after three strikes.
Left on base expand_more
Left on base
Runners stranded when an inning ends.
ERA expand_more
ERA
Earned runs allowed per nine innings by pitchers.
Errors expand_more
Errors
Defensive mistakes that help batters or runners advance.