Balk: An illegal motion by the pitcher with one or more runners on base, entitling all runners to advance one base. A balk can be one of a number of movements related to the pitching motion but the intention is to catch the runners off balance.

Ball: A pitch which does not enter the strike zone and is not struck at by the batter.

Base: The four points of the baseball diamond (first through third bases and home plate) that must be touched by a runner in order to score a run.

Batter: The offensive player who is currently positioned in the batter's box.

Bottom: The second half of an inning.

Bunt: A legally batted ball, not swung at but intentionally met with the bat and tapped within the infield.

Catcher: The defensive player whose position is directly behind home plate.

Defense: The team currently in the field.

Designated Hitter: A player who may be designated to bat instead of the pitcher.

Double: A play in which the batter makes it safely to second base without stopping.

Dugout: The seating area for team members not currently on the playing field.

Fair Ball: A legally batted ball that settles on or over fair territory.

Fair Territory: That part of the playing field within and including the first base and third base lines, from home plate to the playing field fence and perpendicularly upwards.

Fly Ball: A ball which goes high in the air when batted.

Force Play: A play in which a runner loses his right to occupy a base when the current batter becomes a runner.

Foul Ball: A batted ball that lands on foul territory between home plate and first base or third base, bounds past first or third base on or over third territory, first touches foul territory beyond first or third base, or touches a player, umpire or any object not part of the playing field while over foul territory.

Ground Ball: A batted ball which rolls along the ground.

Ground Rule Double: When a line drive bounces on the field and over the wall in fair territory the hit is scored as a ground rule double and the batter advances to second base.

Home Plate: The base over which an offensive player bats, and to which he must return after touching all three bases in order to score a run.

Home Team: The team on whose field the game is played. If the game is played on neutral grounds, the home team shall be designated by mutual agreement.

Infield: The diamond-shaped portion of the playing field bordered by the four bases.

Infielder: A fielder who occupies a position in the infield.

Line Drive: A ball which is batted directly to a fielder without touching the ground.

Outfield: The portion of the playing field that extends beyond the infield and is bordered by the first and third baselines.

Quick Return Pitch: An illegal pitch, made with obvious intent to catch the batter off balance.

Run: The score made by an offensive player who has rounded the bases and returned to home plate.

Runner: An offensive player who is advancing toward, touching or returning to any base.

Safe: A declaration by the umpire that a runner who is trying for a base has not been tagged or forced out, and is therefore entitled to that base.

Single: A play in which the batter safely makes it to first base.

Strike Zone: An area directly over home plate, from the bottom of the batter's kneecaps to the midpoint between the top of the batter's shoulders and the top of the batter's uniform pants.

Tag: The action of a fielder in touching a base with his body while holding the ball, or touching a runner with the ball, or with his hand or glove while holding the ball.

Throw: The act of propelling the ball toward a given objective, usually a teammate. A pitch is not a throw.

Triple: A play in which the batter makes it safely to third base without stopping.

Triple Play: A defensive play in which three offensive players are put out as a result of one action.

Umpire: The official who judges the legality of individual plays and who otherwise enforces the rules of the game.