I tend to write about a lot of statistics on this site. I also tend to pull from many different sites and sources when it comes to the stats I use. Below is a, hopefully, helpful glossary of every statistic or sabermetrically inclined term I have written about on this site. Some are simple, maybe even redundant, while others are complicated. This way at least a tiny window has been opened into what I am choosing to write about.

**At-Bat (AB)**

- Recognized as when the hitter makes a Plate Appearance and doesn’t Walk, get a Hit-by-Pitch, suffer Catcher’s Interference, nor is he/she given credit for a Sacrifice.

**Balls in Play Percentage (BIP%)**

- The percentage of hit balls that win up in the field of play, ie: not foul, not a home run, etc.

**Barrel Percentage (Barrel%)**

- A batted ball event where similar batted balls have led to a minimum Batting Average of .500 and Slugging Percentage of 1.500.

**Base on Balls (BB, Walk)**

- When a batter reaches base because the pitcher threw four pitches outside the strike zone.

**Base on Balls Percentage (BB%)**

- How often a hitter Walks per Plate Appearance.

**Base on Balls per 9 Innings Pitched (BB/9)**

- Number of Base on Balls given up by a pitcher per 9 Innings Pitched.

**Base on Balls to Strikeouts (BB/K, BB/K%)**

- The ratio of Walks to Strikeouts.

**Base Running (BsR)**

- Measures the total output of a player on the basepaths, from stolen bases to extra bases taken.

**Baserunning Runs (BRR)**

- Measures a baserunners ability on the basepaths in all situations and ties it into how many runs a baserunner adds to the team. Averages out Ground Advancement Runs, Air Advancement Runs, Stolen Base Runs, Hit Advancement Runs, and Other Advancement Runs as well as inputs park factors.

**Batted Ball Distance (BBD)**

- How far a ball is hit, measured in feet.

**Batting Average (Average; BA)**

- Perhaps the most widely used statistic in all of baseball, though not among the most revealing. The number of Hits divided by the number of At-Bats.

**Batting Average Against (BAA)**

- The Batting Average of hitters against a specific pitcher.

**Batting Average on Balls in Play (BABIP)**

- The Batting Average of a hitter on balls that land in play, this excludes Home Runs.

**Batting Average with Runners in Scoring Position (RISPBA)**

- The number of Hits divided by the number of At-Bats when runners are in scoring position.

**Caught Stealing (CS)**

- When a baserunner attempts to take an extra base without any batted ball event or a Wild Pitch/Passed Ball, but is thrown out in the process.

**Changeup Percentage (Changeup%)**

- The number of times a pitcher throws their changeup as compared to their other pitches.

**Clutch**

- A measurement of a player’s quality in certain game situations. WPA divided by Leverage Index.

**Complete Game (CG)**

- When a pitcher is in the Game for the entirety that the Game lasts.

**Contact Percentage (Contact%)**

- Percentage of Pitches on which contact was made.

**Contextual Fielding Independent Pitching (cFIP)**

- It takes the standard FIP evaluation, or how a pitcher allows runs independent of any fielding, and adds context to those results. It does so by looking at results on an individual basis, be it a hitter, umpire, pitcher, etc.

**Curveball Percentage (Curveball%)**

- The number of times a pitcher throws their curveball as compared to their other pitches.

**Defensive Runs Saved (DRS)**

- Measures the number of Runs a fielder saves for their team. This could mean plays that a fielder has made on bunts, turning double plays, robbing a Home Run, etc. The metric is represented with a base of 0, meaning that a number above 0 is that many runs better than average.

**Deserved Run Average (DRA)**

- A metric that estimates how much a pitcher contributes to the Runs scored in their appearances. DRA adjusts for park factors, quality of opponent, framing, pitch type, etc. It is graded out in a per innings pitched model and displays accordingly.

**Deserved Run Average Minus (DRA-)**

- An index stat, DRA- establishes a baseline average number of 100 and then a player is either below average or above average depending on if they are above 100 or below 100. All the inputs and measurements of DRA, only displayed so that they adjust to an average of 100 and compare the player to their peers.

**Deserved Runs Created Plus (DRC+)**

- An index stat, DRC+ establishes a baseline average number of 100 and then a player is either below average or above average depending on if they are below 100 or above 100. DRC+ measures Deserved Runs Created, or what the hitter should actually get credit for in his/her At-Bats. It does this by giving the hitter credit for their results, but it also scales how important the results were, as in a Single versus a Home Run, and works in elements such as the quality of the pitcher, park factors, and league. The driving factor in DRC+ is that a player has to consistently deliver the same results to gain the maximum reward for them. The end result is a metric that gives a hitter credit for the Runs he/she is creating for their team with their bat.

**Earned Run Average (ERA)**

- A tried and true pitching metric. Earned Runs allowed over a nine-inning standard.

**Earned Run Average Plus (ERA+)**

- An index stat, ERA+ establishes a baseline average number of 100 and then a player is either below average or above average depending on if they are below 100 or above 100. ERA with park and league factors added to the equation.

**Exit Velocity (EV)**

- How hard a ball is hit, in miles per hour.

**Expected Batting Average (xBA)**

- Exit Velocity, Sprint Speed, and Launch Angle are used to gauge how many of a hitter’s batted balls should actually be Hits.

**Expected Slugging Percentage (xSLG)**

- Exit Velocity, Sprint Speed, and Launch Angle are used to gauge what the Slugging Percentage should be on a batted ball.

**Expected Weighted On-Base Average (xwOBA)**

- Exit Velocity, Sprint Speed, and Launch Angle are combined with Base on Balls, Hit-by-Pitch, and other on-base events to gauge what the Weighted On-Base Percentage should be for a hitter.

**Extra Base Hit (XBH)**

- Any Hit that goes for more than a Single.

**Extra Base Hit Percentage (XBH%)**

- The percentage of Extra Base Hits by a player.

**Fielding Independent Pitching (FIP)**

- A pitching metric that calculates how many Runs a pitcher gives up independent of any fielding. Essentially FIP is gauging how many Runs a pitcher is able to prevent devoid of any help from their defense.

**Fielding Independent Pitching Minus (FIP-)**

- An index stat, FIP- establishes a baseline average number of 100 and then a player is either below average or above average depending on if they are above 100 or below 100. FIP with park and league factors added to the equation.

**Fielding Runs Above Average (FRAA)**

- A defensive metric that uses play-by-play results while also including park factors, batter handedness, pitcher tendencies, and where it’s likely an out could have been made.

**Fly Ball Percentage (FB%)**

- The percentage of balls Hit into the air.

**Fly Ball/Line Drive-Outfield Percentage (FB/LD-OF%)**

- Percentage of fly balls and line drives Hit to the outfield.

**Flyout Percentage (FO%)**

- The percentage of outs that are hit into the air.

**Fourseam Fastball Percentage (Fourseam%)**

- The number of times a pitcher throws their fourseam fastball as compared to their other pitches.

**Game Score**

- A metric meant to relay the overall performance of a pitcher in a game. It is point based with various accomplishments adding to the score.

**Good Baserunning Plays (GBP)**

- A metric that gives a baserunner credit for taking an extra base, beating out a tag, or otherwise taking away an Out that should have been.

**Groundball Percentage (GB%)**

- Percentage of batted balls that are hit into the ground.

**Groundballs per Balls in Play (GB/BiP%)**

- The percentage of balls a pitcher allows to be put in play that are groundballs.

**Groundball-Infield Percentage (GB-IF%)**

- The percentage of balls Hit to the infield that are on the ground.

**Groundball-Outfield Percentage (GB-OF%)**

- The percentage of balls Hit to the outfield that are on the ground.

**Ground Out (GO)**

- Any batted ball event on the ground that results in the batter being Out at first base.

**Hard Hit Percentage (Hard Hit%)**

- Percentage of batted balls that are hit hard, usually better than 95mph.

**Hit (H)**

- Any batted ball event that results in a hitter safely reaching base that does not come about via an Error.

**Hits per Nine Innings Pitched (H/9)**

- Number of Hits given up by a pitcher per 9 Innings Pitched.

**Hit-by-Pitch (HBP)**

- When a batter is hit by a thrown ball that he/she did not swing at.

**Home Run (HR)**

- Any batted ball that allows a hitter to touch all four bases and score, without an Error being assigned.

**Home Run Percentage (HR%)**

- Percentage of balls hit for Home Runs.

**Home Runs per Nine Innings (HR/9)**

- The number of Home Runs allowed by a pitcher over a nine-inning scale.

**Home Run to Fly Ball Rate (HR/FB)**

- The ratio of how many Home Runs a player hits out of their total fly balls, or conversely how many Home Runs a pitcher gives up out of their total fly balls.

**Innings Pitched (IP)**

- The number of innings pitched over any amount of time.

**Inside the Zone Contact Percentage (Z-Contact%)**

- The percentage of pitches inside the strike zone that a hitter swings at and makes contact with.

**Inside the Zone Swing Percentage (Z-Swing%)**

- The percentage of pitches inside the strike zone that a hitter swings at.

**Isolated Power (ISO)**

- A hitter’s extra-base hits per At-Bat, a measure of a hitter’s true power.

**Jaffe WAR Score System (JAWS)**

- A system designed by writer Jay Jaffe to more accurately measure a player’s candidacy to the National Baseball Hall of Fame. JAWS is a player’s career rWAR averaged with their 7-year rWAR peak.

**Launch Angle (LA)**

- The elevation, in degrees, that a hitter is able to get on a ball.

**Left on Base Percentage (LOB%)**

- The percentage of baserunners that a pitcher leaves stranded on base when they record the third Out of an Inning.

**Line Drive Percentage (LD%)**

- The percentage of ball that a hitter drives in a horizontal plane.

**Loss (L)**

- The team that has fewer Runs at the end of the game. When applied to individual players this is a relatively useless metric.

**On-Base Percentage (OBP)**

- A meaty stat, it gives a good indicator of a hitter who understands the strike zone and that there is more to hitting than just making contact. How often a hitter winds up on base through a positive result.

**On-Base + Slugging (OPS)**

- A hitter’s On-Base Percentage plus their Slugging Percentage.

**On-Base + Slugging Plus (OPS+)**

- An index stat, OPS+ establishes a baseline average number of 100 and then a player is either below average or above average depending on if they are below 100 or above 100. A metric that is attempting to quantify the overall production of a hitter. OPS+ takes a hitter’s On-Base Percentage and Slugging Percentage then works in league and park factors. All together this should give a better representation of how much a hitter is contributing to their team’s offense.

**Outfield Jump (OJ)**

- A measurement of reaction time to a hit ball, specifically how many feet did a player cover in the three seconds after the ball was hit.

**Outs Above Average (OAA)**

- The number of Outs an outfielder makes above the league average, set to 0. The number of outs an outfielder makes as well as how many he/she doesn’t are calculated as well as the difficulty of the out achieved.

**Outside the Zone Contact Percentage (O-Contact%)**

- The percentage of pitches outside of the strike zone that a hitter swings at and makes contact with.

**Outside the Zone Swing Percentage (O-Swing%)**

- The percentage of pitches outside of the strike zone that a hitter swings at.

**Plate Appearance (PA)**

- Any At-Bat where a hitter either gets on base or is put Out.

**Player Empirical Comparison and Optimization Test Algorithm (PECOTA)**

- A projection model that uses past historical results and expected player progression to project future outcomes. Chicago Cubs fans favorite projection system.

**Quality Start (QS)**

- When a starting pitcher throws 6+ innings and gives up 3 or fewer earned runs.

**Range Factor per Nine Innings (RF/9)**

- A defensive metric that takes a fielder’s number of Putouts and Assists and divides them by total Innings Played. It is a dated metric, but still useful in unaffiliated leagues where play-by-play data is scarce.

**Run (R)**

- When a baserunner safely crosses home plate to score for their team.

**Run Expectancy (RE)**

- How many Runs are expected to score in a given baserunning situation dependent on how many Outs have been recorded in that Inning.

**Runs Allowed per Nine Innings Pitched (RA/9)**

- The amount of Runs allowed per nine Innings Pitched, including Earned and Unearned Runs.

**Runs Batted In (RBI)**

- Anytime a hitter brings a runner home through a positive result, as in not an Error, double play, etc., the hitter is awarded a Run Batted In.

**Save (S)**

- When a relief pitcher finishes a game that his/her team wins, but they entered the game with their team ahead and pitched either a certain amount of innings or the game was within three Runs when they entered.

**Shutout (SO)**

- When a team fails to score any Runs over the course of a completed game.

**Sinker Percentage (Sinker%)**

- The number of times a pitcher throws their sinker as compared to their other pitches.

**Slash Line**

- A collection of hitting metrics meant to give a better representation of a hitter as a whole. The three metrics are Batting Average, On-Base Percentage, and Slugging Percentage.

**Slider Percentage (Slider%)**

- The number of times a pitcher throws their slider as compared to their other pitches.

**Slugging Percentage (SLG)**

- The ability of a hitter to mash the ball. Total bases divided by At-Bats.

**Speed Score (Spd)**

- A metric that measures a player’s overall speed by averaging their Stolen Base Percentage, Frequency of Stolen Base Attempts, Percentage of Triples, and Runs Scored Percentage.

**Sprint Speed (SS)**

- A baserunners speed as measured by how many feet-per-second they run in their fastest one-second window as well as their top home-to-first times.

**Stolen Base (SB)**

- When a baserunner takes an extra base without any batted ball event or a Wild Pitch/Passed Ball.

**Stolen Base Success Rate (SBSR, SB%)**

- The percentage of times a baserunner successfully steals a base.

**Strikeout (K)**

- Any At-Bat resulting in a batter getting Out without making contact or by foul-tipping the ball into the catcher’s mitt.

**Strikeout Percentage (K%)**

- How often a hitter Strikes Out per Plate Appearance.

**Strikeouts per Base on Balls (K/BB, K/W, SO/BB, SO/W)**

- How many Strikeouts a pitcher records for every Base on Balls they issue.

**Strikeouts per Nine Innings (SO/9)**

- How many Strikeouts a pitcher records for every nine innings pitched.

**Swinging Strike Rate Percentage (SwStr%)**

- Percentage of all pitches thrown that result in a swing and miss from the hitter.

**Swing Percentage (Swing%)**

- The number of times a hitter swings at pitches.

**sZymborski Projection System (ZiPS)**

- A projection model that uses curved grading based on past events to attempt to predict future results for players.

**Total Bases (TB)**

- The total number of bases a hitter attains when registering a hit. This is linear weighted, so a single is worth 1 Total Base, a double is worth two Total Bases, and so on.

**Ultimate Base Running (UBR)**

- A linear weight statistic that attempts to calculate how many runs a baserunner produces for their team without taking into account stolen bases.

**Ultimate Zone Rating (UZR)**

- Quantifies how many Runs a fielder saved or allowed based on their defensive prowess. It uses Outfield Arm Runs, Double-Play runs, Range Runs, and Error Runs to come to its final number.

**Walks and Hits to Innings Pitched (WHIP)**

- One of the first more advanced pitching metrics. Walks and Hits allowed divided by Innings Pitched.

**Weighted On-Base Average (wOBA)**

- A metric that uses linear weights to place a value on how a hitter reached base. Hitters are given credit for any positive result that leads to them being on base, in addition to Sacrifices, but minus Intentional Base on Balls.

**Weighted Runs Created Plus (WRC+)**

- An index stat, WRC+ establishes a baseline average number of 100 and then a player is either below average or above average depending on if they are below 100 or above 100. WRC+ is a way of giving a complete idea of a hitter’s production. WRC+ takes park factors and league into account, and it factors into the results from a Plate Appearance. Bigger results are worth more, but they are all tied together to give a better idea of how a player is producing offensively compared to his or her peers. Specifically just how many Runs a player is giving their team via his/her bat.

**Whiff Rate (Whiff%)**

- Swings and misses as a percentage of swings.

**Wild Pitch (WP**)

- Whenever a pitcher makes an errant throw to a batter that the catcher is not able to handle allowing runners to advance.

**Win (W)**

- The team that has more Runs at the end of the game. Used for individual player statistics it is a near useless metric.

**Win Probability Added (WPA)**

- A metric that credits a player for increasing or decreasing their team’s chances of winning the game. This is dependent on game situation, score, inning, etc.

**Wins Above Replacement (bWAR, dWAR, fWAR, rWAR, sWAR, tWAR, WAR)**

- An attempt to calculate the total value of a player, or how many Wins a player adds over a traditional replacement player. This takes into account the totality of the player: pitching, hitting, fielding, and baserunning. The baseline number is always 0. Obviously, there will be different formulas and results for pitchers and hitters, but ultimately the statistic is trying to find how many Wins a player brings to their team, or how many wins a player costs their team as WAR can have negative results. There are also different versions of WAR: Baseball Prospectus=bWAR, DeltaGraphs=dWAR, FanGraphs=fWAR, Baseball Reference=rWAR, Seamheads Negro Leagues Database=sWAR, Statiz=kWAR, and CPBL Stats=tWAR. While calculated differently depending mainly on which index stats the site in question uses, the end result is still a metric that states how many Wins better or worse a player is than a replacement level player.

**sZymborski Projection System (ZiPS)**

- A projection model that uses past historical results and expected player progression to project future outcomes.