The game is played in nine innings in which each team gets one
turn to bat and try to score runs while the other pitches and
defends in the field. In baseball, the defense always has the
ball -- a fact that differentiates it from most other team sports.
The teams switch every time the defending team gets three players
of the batting team out. The winner is the team with the most
runs after nine innings. In the case of a tie, additional innings
are played until one team comes out ahead. At the start of the
game, all nine players of the home team play the field, while
players on the visiting team come to bat one at a time.
The basic contest is always between the pitcher
for the fielding team, and a batter. The pitcher throws—pitches—the
ball towards home plate, where the catcher for the fielding team
waits to receive it. The batter stands in one of the batter's boxes
and tries to hit the ball with a bat. The catcher's job is to catch
any ball that the batter misses or does not swing at, and, most
importantly, to "call" the game by a series of hand signals
to the pitcher what pitch to throw and where. If the pitcher disagrees
with the call, he will "shake off" the catcher by shaking
his head no; he accepts the sign by nodding. The catcher's role
becomes more crucial depending on how the game is going, and how
the pitcher responds to a given situation. Each pitch begins a
new play, which might consist of nothing more than the pitch itself.
Each half-inning, the goal of the defending team is to get three
members of the other team out. A player who is out must leave the
field and wait for his next turn at bat. There are many ways to
get batters and baserunners out; some of the most common are catching
a batted ball in the air, tag outs, force outs, and strikeouts.
After the fielding team has put out three batters, that half of
the inning is over and the team in the field and the team at bat
switch places. Thus, a complete inning consists of each opposing
side having a turn on offense.
The goal of the team at bat is to score runs; a
player may do so only by batting, then becoming a base runner,
bases in order (via one or more plays), and finally touching home
plate. To that end, the goal of each batter is to enable baserunners
to score or become a baserunner himself. The batter attempts to
hit the ball into fair territory—between the foul lines—in
such a way that the defending players cannot get them or the baserunners
out. In general, the pitcher attempts to prevent this by pitching
the ball in such a way that the batter cannot hit it cleanly.
A baserunner who successfully touches home plate after touching
all previous bases in order scores a run. In an enclosed field,
a fair ball hit over the fence on the fly is normally an automatic
home run, which entitles the batter and all runners to touch
all the bases and score. A home run hit with all bases occupied
is called a grand slam.