MLB London Series: Baseball rules explained for New York Yankees v Boston Red Sox

• MLB London Series: How to watch on TV or live stream for FREE online – dates, times, stadium details

If you’re thinking about watching the games on BT Sport or iPlayer this weekend but you're new to the game, we've got you covered.

RadioTimes.com has rounded up all the rules and everything you need to know to enjoy the MLB London Series.

How many baseball teams are there?

There are 30 Major League teams. Major League Baseball is made up of two ‘leagues’, the American League (AL) and the National League (NL), which are split into three divisions each—East, West and Central. All but one team—the Toronto Blue Jays—are based in the United States.

How many games do MLB teams play?

Baseball teams play an astonishing 162 games per season, from late March/early April through late October/early November.

Teams primarily play opponents within their own league, though they've played between 15 and 20 interleague games since 1997.

How does an MLB team win a championship?

The top teams qualify for the postseason, which has a bracket structure.

The American League and National League champions play each other in the World Series, a best-of-seven to determine who gets to lift the Commissioner’s Trophy.

Is the MLB London Series important?

Both the Yankees and Red Sox are in the AL East Division. Their rivalry—the closest thing baseball has to a derby—is arguably the most famous in the sport.

The Yankees are currently sitting in first place in the division, a surprise to a lot of people, particularly as so many of their star players have been injured this season. They're also on a hot streak, winning nine of their last ten games.

The Red Sox, last year's World Series champions, are in third place.

We're just approaching the halfway point in the season, so there's still a a lot to play for.

How does baseball work?

Baseball has nine innings. Each inning is broken up into two halves, called the top and the bottom.

The home team (in this case, the Boston Red Sox for both games) fields in the top of the inning and bats in the bottom.

You may have heard the song “Take Me Out to the Ballgame”.

It’s sung in the middle of the seventh inning, during the 'seventh-inning stretch', a beloved tradition across the game:

What does a baseball field look like?

A baseball field is also called a diamond because of the shape of the infield. Batters start at home plate, then must touch first, second and third bases before coming home again to score a run (more on that later).

There is also the outfield area, which, as you might guess, is the area beyond the infield—pretty much where the dirt becomes grass in this picture:

Major League Baseball stipulates that the infield must be a square that is 90 feet on each side. The pitcher’s mound, in the middle of the square, must be ten inches above the level of home plate and 60 feet, six inches away from the back of it.

The field is framed by foul lines, also called the first baseline and third baseline, which you can also see marked on the field. Generally speaking, if a ball is hit in fair territory (called a fair ball) it is in play. If it is hit in foul territory (foul ball) the ball is out of play.

Stadiums also have foul poles in the outfield stands to determine whether or not a hit is a home run (more on those later):

What are the fielding positions? How many fielders are there?

There are nine defenders on the field:

Infielders include the first, second and third baseman as well as the shortstop, who is generally positioned somewhere between second and third base. A base is also sometimes called a bag.

The pitcher throws the ball off the mound to the catcher, who crouches behind home plate. Together, they are referred to as the battery. Teams can—and almost always do—use multiple pitchers during a game. Once a player is taken out of the game and replaced, he can't come back.

There are also three outfielders, which are named from the batter’s perspective: the left fielder, centre fielder and right fielder.

What kinds of pitches are there? How fast do they throw?

There are different kinds of pitches you might hear about, like fastballs, curveballs, sinkers and sliders, which vary in grip and delivery. Most pitchers have a few of these in their arsenal and vary them throughout an at-bat.

A strike is a pitch that crosses home plate in a batter’s strike zone. MLB’s definition is more specific, but a good phrase to remember is “knees to letters” – the area from around the player’s kneecaps to the letters on his jersey, and over home plate.

A ball is anything thrown outside the strike zone. After four balls, a batter can walk to first base.

Batters can also take first base if they get hit by a pitch, which can hurt: the average fastball speed for an MLB pitch is over 90 miles per hour. Some, like the St Louis Cardinals' Jordan Hicks, regularly hit 100 miles per hour!

How does an inning work?

A half-inning ends after the defending team gets three outs. Then, the fielders bat and vice versa.

How does a team record an out?

This can be done in a number of ways. Here are some of the most common:

A catch: If a ball is hit in the air, doesn’t touch the ground and is caught by a defender, the hitter is out. This includes balls hit into foul territory—or the stands—which can result in some spectacular catches:

A strikeout: even non-baseball fans have probably heard it: three strikes and you’re out. A batter gets a strike when he swings and misses or doesn’t swing at or hit a pitch in his strike zone. Balls and strikes are determined by the umpire.

Here, too, there’s a weird foul ball exception: the first two foul balls hit count as strikes, but a player can’t strike out on a third foul. This can be especially confusing to a new viewer!

Out on base: If a batter hits a ball into fair territory, he has to run to first base. If he believes he’s hit it hard or far enough, he can also try to take additional bases—that’s how we get terms like hitting a single, double, or triple.

Tagged out: If a runner isn’t standing on a base, or if he is running between bases, he can also be tagged out (see the next question).

What is a force out?

This can be one of the most confusing rules, but it's also one of the key ones to understand.

A batter/runner is forced to run, in simple terms, if he’s hit the ball into fair territory and has to run to first base, if he’s on first and the batter gets a hit or a walk, or if he’s on another base and all the bases before his are occupied.

When a player is forced to run, all a defending player needs to do is touch the base the runner is aiming for while holding the ball to get him out.

If a runner isn’t forced to run but chooses to, he needs to be tagged out by a defender—the defender needs to touch the runner with his hand holding the baseball, or with his glove with the baseball in it, like this:

How is a run scored?

A run is scored when a player has rounded all the bases and touched home plate.

What is a home run?

A home run is, generally, a ball hit beyond the outfield in fair territory (remember that foul pole?). After a home run, the batter (and anyone occupying the bases) all get to round the bases and come home.

Home runs can an also be called dingers, homers, blasts, bombs, jacks, and a bunch of other fun terms.

What is a grand slam?

A grand slam is a home run hit when all the bases are occupied, so a four-run home run.

How does a team win? When does a baseball game end?

A regulation game ends in the ninth inning, either after the third out in the top (if the home team is winning, they don’t need to bat again!), or the third out in the bottom, if the home team is behind heading into the ninth.

The team with the most runs wins.

What if there's a tie?

They keep playing until someone wins, so when they have more runs after both halves of an extra inning are played.

Wait, does that mean…?

It sure does. There is no time limit to a baseball game. The average MLB game takes about three hours, but eight games in MLB history have lasted more than 22 innings. The longest by time? Eight hours and six minutes.

Baseball terms and phrases

Here are some other things you'll probably hear the commentators say:

Bullpen: the place pitchers warm up.

The count: the number of balls and strikes on a batter in an at-bat, in that order. So a 2-1 count means the batter has two balls and one strike on him. A full count is 3-2.

Designated Hitter: Or the DH. In the National League, pitchers bat. In the American League, they are replaced by a Designated Hitter, a player who does not field. This is an American League game, so there will be a DH on both teams.

The dugout: the place the team sits when they're not fielding or batting.

Double/triple play: it's possible for the defending team to record two or more outs on the same play. A well-executed double or triple play can be one of the most impressive things to see in baseball:

ERA stands for Earned Run Average. It's a pitching statistic: the lower a pitcher's ERA the better.

Fly ball/pop fly: a ball hit high into the air. If caught, the hitter is out and runners return to the bases they were standing on before the ball was hit.

Ground ball or grounder:exactly what it sounds like! A ball hit on the ground.

On deck: the next batter up

RBI stands for Runs Batted In. A batting statistic, so the higher the better, this time!

Starting pitchers are the ones who start the game and generally pitch for the most innings. Relief pitchers replace them.