An inning consists of batters from each team taking their turn at bat until three batters are out. A game lasts nine innings, but is extended into extra innings if the scores are level.

The fielding side consists of a pitcher, catcher, four infielders, and three outfielders.

The pitcher throws overhand, using a variety of deliveries from a raised mound to the home plate - a distance of 60.5ft (18.4 m).

An opposing batter attempts to hit the pitches and then get on base, while the fielders attempt to get the batter out through various plays.

A run is scored every time a batter becomes a runner and crosses home plate after touching each base in the prescribed order.

When the fielding team gets their opponents' three batters (or runners) out, the teams swap roles.

If the score is level after nine innings, play continues into extra innings until one team has scored more than the other in an equal number of turns at bat.

THE MAJOR LEAGUES

The Majors are two leagues - American and National - each has three divisions: West, Central and East.

Every team plays every other in their league, and they play more games against those in their division. The leagues don't meet until the World Series, apart from a few specially created interleague games.

The leagues also play an All-Star exhibition game during the mid-season break, with teams selected by a fans' ballot.

Each team plays 162 regular season games. They play each other in three or four-game series, and teams often play a string of these away on a road trip.

Each league's three divisional winners are joined by one wild card to make up the league semi-finals, followed by best-of-seven league finals and then the World Series, also known as the Fall Classic.

KEY TERMS - BATTING

AT BATS (AB): Turns at batting. Normally four or five per game for a starting outfield player.

HITS (H): Any time a player connects with the ball and gets to at least first base. This is the most important statistic for a non-pitcher. Included among hits are those termed a bunt or sacrifice bunt, where a batter doesn't swing at the ball pitched to him but turns to face the pitcher straight on and uses the bat to knock the ball down into the ground. A bunt may be used in order to adavance a runner on base or to score by forcing the fielding team to try to play the ball and get the batter out rather than a player who is closer to scoring.

You don't get a hit if a fielder makes a mistake, known as an error , or decides to throw to another base to get somebody else out, a fielder's choice.

Getting to first is called a single, second a double, third a triple (quite rare), and all the way around is a home run. But they all count as one hit.

BATTING AVERAGE (AVG): As in cricket, this is the key measure of player's worth. In short, this is hits divided by at bats.

The average is calculated as a fraction of one, ie. 0.300 (the benchmark of a good player) means the batter gets a hit in 30% of his at bats. Hence, you may see references to a player's average being .300.

Batting averages do not include getting on base via a walk - when the pitcher throws four pitches, or balls outside the strike zone.

Also not counted are sacrifice flies (when a batter hits the ball far enough for a player to score after the catch has been made), sacrifice bunts, being hit by the pitch (which gives you first base), and fielder's choices or errors.

A good batting average is anything over .300; a decent one is about .260; anything below .240 is poor.

Pitchers bat only in the National League (the American League uses designated hitters in their place), and like bowlers in cricket they tend to bat at the end of the nine-man order.

ON BASE PERCENTAGE (OBP): Like the above but includes all those other bits too. A good OBP is .400 - anything below .300 is bad.

STOLEN BASE (SB): Once on base, fast-running players will try to steal a base - normally from first to second, as second base is the furthest throw for the catcher to make from behind home plate.

The player on base starts running as soon as the pitcher begins his action. If the pitcher attempts to break his action by throwing to base instead of the plate it is called a balk, which advances players on base.

SBs are important because if a player gets to second base he can normally get home for a run on a base hit.

A pitcher can try to stop people stealing bases by keeping them close to first base.

The runner will try to get a good head start by going as far from first base as he dares.

But if a pitcher can throw the ball to the first baseman before the runner gets back to the bag, the fielder can tag the him out. This is called a pick off.

RUNS BATTED IN (RBI): After batting averages, this is the most important batting stat. You get an RBI every time you enable someone to score.

So, if you hit a home run you get one because you have scored. If you get hit by the pitch when the bases are loaded (players on first, second and third), you get an RBI as everyone has to move around one base. If you hit a home run with the bases loaded (a grand slam) you get four RBIs.

KEY TERMS - PITCHING & FIELDING

EARNED RUN AVERAGE (ERA): After their win-loss record, this is the key stat for pitchers (akin to bowling averages in cricket).

An ERA is how many runs a pitcher gives up per nine innings. Runs scored by players who got on base due to an error are not his fault and therefore unearned - a bit like byes on a bowling average.

A good ERA is anything below 4.00 (ie four runs per nine innings), a bad one is 6.00+.

SAVES (SV): Not every pitcher is a starter - most teams have a rotation of 4-5 starters. The rest of the pitching staff or bull pen (usually 10-12 players) are known as relievers .

When the starting pitcher gets tired or is having an off day, a team manager calls in a reliever.

If the team was still leading when the starter retired, you are attempting to complete the win and earn a save.

A pitcher only earns a save if the lead he inherits is three runs or less, and he has to pitch at least a full innning.

The best relievers will normally only pitch the last innings. If the reliever lets the opposition win, that is a blown save. Relievers that bail out starters by pitching for two or more innings are called middle relievers.

A starter going all the way to the end pitches a complete game. If he does this without giving up a hit that is a no-hitter, which is very rare. Even rarer is a perfect game - no hits or walks, just 27 straight outs.

STRIKEOUTS: Three strikes and you're out. The only complicating factor is foul balls. If the batter hits the ball behind the tramlines that extend into the stands from the lines marking first and third base this is called a foul.

This counts as a strike against the batter, but only up to two strikes. The only way you can foul out is by fouling a bunt - the baseball equivalent of a drop shot in tennis - attempt on two strikes. This is very rare.

Balls are pitches outside the strike zone (over the plate between the batter's knees and chest) - four of those and you get a walk.

A hit batsman speaks for itself - the result is the same as a walk.

A wild pitch is when the pitcher misses his target making it impossible for the catcher to do his primary job.

If he misses a catch he should have held, allowing a runner or runners to advance, this is known as a passed ball (PB).

DOUBLE PLAY (DP): In a bases loaded situation, if you're on first and the batter hits the ball, you have to start running.

If the ball fails to get past the infield (the innermost four fielders) there is a good chance that they can get the man on base out and still have time to throw to first to get you out. A triple play is very rare.