Baseball Rules – Complete Guide
A complete overview of baseball rules, from game structure to key terms.
Baseball Glossary
At bat (AB)
An official turn for a player at the plate.
Batting average (AVG)
The ratio of valid hits to at-bats.
Bullpen
The area where relief pitchers warm up.
Closer
A pitcher specializing in finishing games at the end.
Double
A hit that allows the batter to safely reach second base.
Double Play
A defensive play in which two offensive players are put out as a result of one continuous action.
ERA (Earned Run Average)
The average of earned runs allowed by a pitcher per nine innings.
Fielder's Choice
A play where a fielder, after fielding a ground ball, chooses to put out a preceding runner rather than the batter.
Fly Out
An out that occurs when a batter hits a ball that is caught by a fielder in the air.
Foul ball
A batted ball hit outside the fair territory.
Ground Out
An out made when a batter hits the ball on the ground and is thrown out at first base.
Ground rule double
A ball that bounces and leaves the field → batter goes directly to 2nd base.
Hit by Pitch
When a batter is struck by a pitched ball without swinging at it. The batter is awarded first base.
Home Run
A fair ball hit out of the playing field. The batter and any runners on base are awarded a run.
Line drive
A hard-hit ball in a straight line.
No-hitter
A game in which a pitcher does not allow any hits.
Perfect game
A pitcher retires 27 batters without anyone reaching base.
Pinch hitter
A player who comes in to bat in place of another.
RBI (Runs Batted In)
Runs scored as a result of a hit.
Reliever
A substitute pitcher who enters during the game.
Sacrifice Bunt/Fly
A play where a batter intentionally gets out to advance one or more runners.
Single
A hit that allows the batter to safely reach first base.
Stolen base
A successful base steal.
Strikeout
An out recorded when a batter accumulates three strikes.
Triple
A hit that allows the batter to safely reach third base.
Walk (Base on Balls)
Awarding a batter first base, after the pitcher throws four pitches outside the strike zone.
Walk-off
A play that ends the game immediately, usually a home run by the home team in extra innings or the 9th.
Practical Examples
Walk-off Home Run
Game tied 2-2 in the 10th inning, a home team batter hits a home run → final score 3-2 and the game ends immediately.
Triple Play
Bases loaded with no outs, ball hit to the third baseman, who steps on 3rd (out 1), throws to 2nd (out 2), then to 1st (out 3).
Grand Slam
A batter hits a home run with the bases loaded → 4 runs at once.