A breaking ball in baseball is also known as breaking pitches, these pitches curve in a certain direction while in flight -- they can have an arced path, travel toward the ground, or curve to the left or right. Their purpose is to trick batters. This type of pitch includes curveballs, forkballs, splitters, sliders, and backdoor sliders.
Breaking pitches (more commonly known as breaking balls) are pitches that, unlike fastballs, "break" from a straight path through the air. This means that they curve in a certain direction while in flight -- they can have an arced path, travel toward the ground, or curve to the left or right. Their purpose is to trick batters. For example, at first a pitch may seem like it has a straight path, and the batter might swing at it. Then, when it is too late for the batter, the ball breaks directions and the batter misses the baseball. Breaking balls are more difficult to hit than fastballs since their path is less predictable; however, they are also more prone to being balls since their path can cause them to miss the strike zone. They also tend to have lower velocities than fastballs. Breaking ball is also used as an umbrella term for more specific types of pitches.
There are few types of breaking pitches that we'll discuss:
A changeup in baseball is a type of pitch thrown by the pitcher that is different in speed, often slower than the previous pitch but has the appearance and path of a fastball, deceiving the hitter and causing him to mistime his swing.
With a changeup pitchers change the pace of a pitch. A pitch does not have to only change directions in order to deceive batters. Differing or slow velocities can also be used to make pitches harder to hit; these types of pitches are called off-speed pitches. Changeups are a common type of off-speed pitch. They look very similar to a fastball -- they are thrown in a similar way and have a straight path -- but are significantly slower than a fastball. While fastballs are usually 90 MPH or above, changeups are usually only 70-80 MPH. For batters, it is often difficult to detect the difference between a fastball and a changeup, since they have the same path and the speed of the baseball cannot be determined until it is very close to the batter. That is why changeups are so effective: They trick batters into thinking the pitch is a fastball, and the batter will swing at it. However, since changeups are much slower than fastballs, the swing would be too early, either missing the baseball completely or hitting it weakly.
Batters can recognize the type of pitch a pitcher is throwing by looking at the seams of the ball. Curveballs are a type of breaking ball that have a forward spin and typically break downward, which means they initially seem to have a straight path, then suddenly travel downward. However, some pitchers will add variants to this general principle. Curveballs are relatively slow, usually between 70-80 MPH in the Majors, but they have a high amount of movement compared to other pitch types.
Fastballs are the most basic and the most common type of pitch that pitchers throw. As the name suggests, its main quality is speed, so it has a relatively straight path compared to other pitch types. Fastballs are usually the first pitch a pitcher throws to a batter in any at-bat. This helps the pitcher gauge the batter's reaction time as well as determine the strike zone for the batter (if the pitcher throws a straight fastball in what he thinks is the batter's strike zone but the umpire calls it a baseball, the pitcher will have to adjust for the rest of the at-bat). In Major League Baseball, fastballs nearly always reach velocities of 90 miles per hour or above. The speed of the pitch is measured by a device called a radar gun. After each pitch, the radar gun reading is usually displayed on screens around the stadium.
A forkball in baseball is a type of pitch that is similar to a curveball, but more extreme. Forkballs break downward, but their break is much more extreme and sudden than a typical curveball. They are a rare type of pitch due to the tiring and risky motion used to throw them.
Forkballs are a rare type of breaking pitch. They are like an extreme form of curveballs in that they break downward, but their break is much more extreme and sudden. Throwing forkballs requires the pitcher to snap his wrist, which can be tiring and may cause injury, and contributes to why pitchers rarely (if ever) throw forkballs.
A splitter in baseball is a type of breaking pitch that looks like a fastball, but is slightly slower (usually between 80-90 MPH) and breaks downward suddenly before reaching home plate. It is designed to deceive batters into swinging off-time.
A much more common derivative of the forkball is the splitter. They are slightly slower than a fastball, usually between 80-90 MPH, and they break downward suddenly before reaching home plate. However, their break is not as extreme or sudden as a forkball, making them easier to throw and less susceptible to causing injury.
A slider in baseball is a type of pitch that has lateral (left/right) movement while also breaking downward. Typically has higher velocity but less movement than a curveball.
Sliders are similar to curveballs -- they tend to break downward, however, they typically have more lateral (left/right) movement and have higher velocities than curveballs. They also tend to have less movement than curveballs; that is, their break from a straight path is not as dramatic. Breaking balls like curveballs, forkballs, and splitters deceive the batter by pretending to be strikes that the batter might swing at, then change directions so the batter misses the ball. Backdoor breaking balls (often called backdoor sliders, although the term can apply to either curveballs or sliders) operate in the opposite way. Their path is initially lateral, traveling away from the strike zone. The batter thinks it is a ball, and does not swing. Then, at the last second, the pitch curves in and travels through the corner of the strike zone, becoming a strike.
Knuckleballs are rare pitches that use both unpredictable speed and movement to challenge batters. Knuckleballs have minimal rotational spin, causing them to have erratic movement (since spin is what helps determine a ball's motion and direction). A knuckleball's movement is very unpredictable and uncontrollable; it is influenced by factors such as the wind and air resistance. Not only does the knuckleball's erratic movement make it hard for batters to hit, but it is also hard for catchers to catch and umpires to call. Mastering the knuckleball is also difficult for pitchers and not very practical, which is why knuckleballs are so rare.
A screwball in baseball is a type of pitch that moves in the opposite direction of a pitcher's typical curveball or slider. It is a very rare.
A backdoor slider is also known as a backdoor breaking ball, this pitch type excels at deceiving the batter into thinking it is a ball by traveling laterally away from the strike zone and then at the last moment curving back into the strike zone for a strike.
A cutter in baseball is a type of pitch that looks similar to a fastball, but breaks in the opposite direction that a fastball would. Fastballs usually break in the direction of the pitcher's throwing arm side, but cutters cut in the opposite direction of the pitcher's throwing arm side, catching batters off-guard.
A palmball in baseball is a type of pitch that resembles an off-speed pitch or changeup.
A two-seam fastball in baseball is a type of fastball that is one of the common pitches in baseball. It varies slightly from the four-seam fastball in that it tends to have slightly lower velocity and break more.