Sabermetrics: Glossary of Terms

I originally composed the following glossary of terms for posting to RotoExperts.com. Now that they have moved to the new site configuration, this is no longer available. Since that’s the case, I decided to share with you here instead, but not until adding FIP, which was not commonly used when this was first aggregated.

Please touch base with any questions or issues you see below.

 

Acronym Term Definition Formula(s)
2B Double A hit where the batter safely reaches second base without assistance from an error and without advancing from first to second base due only to a fielder’s choice play.
3B Triple A hit where the batter safely reaches third base without assistance from an error and without advancing from first or second base due only to a fielder’s choice play.
AB At Bats How many times a batter comes to the plate without taking a walk. H+K+Outs
AO Air Outs Outs resulting from FB.
Avg Batting Average Indicator of a hitter’s success rate. (Also BA) H/AB
BA Batting Average Indicator of a hitter’s success rate. (Also Avg) H/AB
BAA Batting Average Against Indicator of a Pitcher’s performance that measures how well hitters perform against that pitcher.
BABIP Batting Average on Balls in Play Also known as Hit Rate (H%), BABIP measures the percentage of balls that are hit into the field of play that result in a H, effectively measuring the impact of luck on performance (applies to both pitchers and batters). BABIP removes HR and K from the equation to focus on only balls hit fair and into play. The league average BABIP hovers around 0.300, so batters with a higher BABIP are likely to slump, while those with a lower BABIP are due for a hot streak. For Batters: (H-HR)/(AB-HR-K+SF)
BABIP Batting Average on Balls in Play Also known as Hit Rate (H%), BABIP measures the percentage of balls that are hit into the field of play that result in a H, effectively measuring the impact of luck on performance (applies to both pitchers and batters). BABIP removes HR and K from the equation to focus on only balls hit fair and into play. The league average BABIP hovers around 0.300, so batters with a higher BABIP are likely to slump, while those with a lower BABIP are due for a hot streak. For Pitchers: (H-HR)/((IP*2.82)+H-K-HR)
BB Base-on-Balls Walks, resulting from a PA that ends with a fourth called ball.
BB% Walk Rate Percentage of walks compared to how many times a batter appears at the plate. BB/(AB+BB)
BS Blown Save A BS is charged to an RP when he enters a game in a save-eligible situation and allows the tying run to score. Depending on the ultimate outcome of the game, said RP could also be charged with a Loss if the team loses the game, or he could be credited with a win if the team comes back in the next AB to win the game.
CG Complete Game A complete game is recorded when an SP throws every pitch from start to finish.
Cmd Command Sabermetric term that rates how well a pitcher is able to pitch stikes effectively. The higher the command ratio, the better the pitcher is performing. K/BB
CS Caught Stealing Failure to successfully steal a base.
CT% Contact Rate Measures how well a hitter is able to contact pitches and hit into the field of play. Hitters with high contact rates tend to perform well in BA. (AB-K)/AB
Ctl Control Sabermetric term that rates how well a pitcher controls the strike zone, measured as walks per nine innings (BB/9). BB/IP*9
Dom Dominance Sabermetric term that rates how well a pitcher dominates batters, measured as strikeouts per nine innings (K/9). The best pitchers exhibit dominance rates of at least 6.0. K/IP*9
ER Earned Run A run that was scored without the assistance of a defensive Error.
ERA Earned Run Average Measurement of the average number of ER a pitcher yields per nine IP. (ER/IP)*9
Eye Batting Eye Indicator of a hitter’s ability to control the strike zone. High BA hitters will tend to be near or above 1.0. BB/K
FIP Fielding Independent Pitching Next evolution of deep analysis beyond BABIP, where the impact of fielding quality (or lack thereof) is incorporated to illustrate the “true” skill level at which a pitcher is performing. (((13*HR)+(3*BB)-(2*K))/IP)+3.10
FB Flyball
FB% Flyball Percentage FB% measures the percentage of balls hit in fair territory (inclusive of HR) by a batter that are flyballs.
GB Groundball
GB% Groundball Percentage GB% measures the percentage of balls hit in fair territory (inclusive of HR) by a batter that are groundballs.
GO Ground Outs Outs resulting from GB.
GO/AO Ground Out/Air Out Ratio
H Hits A situation where a batter makes contact with a pitch, driving it into fair territory, and reaches first base safely.
H/9 Hits Per Nine IP A measure of how many H a pitcher yields, normalized to nine innings for comparison purposes.
HR Home Runs Occurs when a batter makes contact with a pitch and drives the ball out of the park in fair territory, effectively driving all baserunners and the batter home for a run each.
HR/9 Home Runs Per Nine IP A measure of how many HR a pitcher yields, normalized to nine innings for comparison purposes. The best pitchers typically keep HR/9 below 1.0.
IP Innings Pitched How many outs a pitcher forces divided by three. For fractions of innings, IP uses 0.1 and 0.2 to indicate one or two outs, but not a complete inning. For example, if a pitcher goes six innings plus forces two outs in the seventh inning, he is credited with 6.2 IP.
K Strikeout When a batter accumulates three strikes in an AB, he is called out, resulting in a K for both the batter (received) and a pitcher (dealt).
L Loss A statistic that is charged to a pitcher when he yields the deciding run, whether earned or unearned, in any game.
LD Line Drive
LD% Line Drive Percentage LD% measures the percentage of balls hit in fair territory (inclusive of HR) by a batter that are line drives.
OBP On-Base Percentage Measures how often a batter reaches first base on H or BB as a percentage of total PA. Also OBA, for On-Base Average. (H+BB)/(PA)
OPS OBP plus SLG On-base Percentage plus Slugging Percentage (OBP + SLG) ((H+BB)/PA) + (TB/AB)
PA Plate Appearances How many times a batter appears as a hitter and completes a play, inclusive of all hits, outs, and walks. Appearances that are cut short due to another out (i.e. a pick off of a man on base) are omitted from PA. AB+BB
QS Quality Start Measure of a pitcher’s isolated pitching performance. A QS occurs when a pitcher starts the game, completes a minimum of six IP, and yields no more than three ER.
RP Relief Pitcher Any pitcher who is brought in after the game starts is an RP for that game.
S Save An RP, typically the closer, earns a save when the following conditions are met (as stated in the MLB rule book):

  1. He is the finishing pitcher in a game won by his team
  2. He is not the winning pitcher
  3. He is credited with at least half of an inning pitched
  4. He satisfies one of the following conditions:
  • He enters the game with a lead of no more than three runs and pitches for at least one inning
  • He enters the game, regardless of the count, with the potential tying run either on base, at bat, or on deck
  • He pitches for at least three innings
S% Strand Rate Percent of ER-eligible base-runners that a pitcher leaves on base when he successfully ends an inning with three outs. (H+BB-ER)/(H+BB-HR)
SB Stolen Base
SB% Stolen Base Percentage Percent of attempted SB that are successful SB/(SB+CS)
SLG Slugging Percentage Measures the power, or extra-base output of a batter. TB/AB
SP Starting Pitcher The person who throws the first official pitch in any given baseball game.
TB Total Bases Measure of how many bases a batter accumulates off of all hits, exclusive of advancement past first base due to defensive error or fielder’s choice. H+2B+(3B*2)+(HR*3)
W Win A statistic that is credited to the pitcher who is in the lineup when a team takes a lead that is never relinquished. For an SP to get a win, he must last at least 5 IP and leave with his team winning, followed by no subsequent tie or change in lead. Any pitcher who appears in a game can be credited with a win in the right circumstances. Since wins are highly dependent on run support, defense, and luck, it is a highly volatile statistic from year-to-year and very difficult to successfully predict.
WHIP Walks & Hits Per Inning Pitched Stat that keeps track of how many people pitchers allow on base via walk or hit in an average inning. High WHIP pitchers tend to have higher ERAs. (BB+H)/IP