Battery - The pitcher and catcher.

Bottom of the 1st, 2nd... the second half of the innings

Breaking ball - when the ball changes direction in the air

Batting average - the number of hits divided by number of times a player has batted. It is always calculated to three decimal places (for example .123)

Bunt - the ball is tapped gently into the infield

Designated hitter - where a player bats instead of the pitcher, and does not field

Diamond - that part of a baseball field that makes up the infield

Double - when a batter reaches second base from one hit

Double header - two scheduled matches played one after the other

Earned run average - the number of runs scored compared to how many innings a pitcher has pitched for

Error - when a fielder makes a mistake that would normally have put a runner out

Fake - a pitcher pretends to pitch but turns to try and stop a runner from stealing base

Force play - when a batter becomes a runner, so all runners are forced to advance

Grand slam - when a batter scores a home run with a player on each base, scoring four runs in one go

Ground ball - a batted ball that travels along or close to the ground

Line drive - a ball hit hard in a straight line

Loaded base - when a base is occupied

No hitter - when the pitcher has not given any runs away

Pinch hitter - substitute batter

RBI - runs batted in, where players are credited with runs scored as a result of their hit, whether they run or other players do. All players concerned are credited with runs

Retouch - when a batter returns to base

Run down - when the defensive team puts out a runner between bases, also called 'caught in the hot box'

Safe - an umpire call when a runner has made a base

Single - when a batter reaches first base from one hit

Squeeze play - when a team has a runner on third base they can score that runner by the batter playing a bunt

Switch hitter - when a batter can hit the ball using either hand

Tie game - a game that is level after the ordinary number of innings

Top of the 1st, 2nd... the first half of an innings

Triple - when a batter reaches third base from one hit

Wild pitch - a pitch too high, low or wide for the catcher to catch