Airmail a green. Hit a ball too far, so that it flies over the green.
Approach shot. A shot from several yards off the green which is expected to reach the green. Approach distance is the distance to the hole after the shot.
Asymptote. A line or other curve to which a given curve becomes infinitely close.
Back nine. The last nine holes on a golf course. This is preceded by the “front nine” to make a round of 18 holes.
Backspin. The most common spin on a golf shot. Viewed from behind, a ball with backspin rotates such that the top of the ball moves directly toward the golfer. The spin vector is to the right.
Back tees. On a hole with several locations for tee shots, the back tee is the tee location that is farthest from the hole. Most courses have back tees (also called “the tips”), white tees (for average golfers), gold tees (for seniors), and red tees (for women).
Bag. The golf bag that holds the golfer’s 14 clubs, balls, and accessories used during a round. If you’re Rodney Dangerfield in Caddyshack, it also holds a keg.
Ball speed. The initial speed of the ball, immediately after contact.
Bernoulli trial. An experiment in which the random outcome can be one of two values, such as a made putt or missed putt. In a sequence of Bernoulli trials, the outcomes are independent and identically distributed (e.g., the probability of making each 5-foot putt is the same and does not depend on whether other 5-foot putts have been made or missed).
Best ball. A team competition in which the team score on a hole for each two-player team is the better of the scores of the individuals on the team. Usually, match play determines the winner.
Best-fit line. A line that comes closest to fitting the points in a data set, where “closest” usually means that the sum of the squares of the errors is minimized.
Bethpage Black. A public course in New York that has hosted the 2002 and 2009 U.S. Opens. It is long and tough, and proud of it. Highly visible signs are posted reading, “The Black Course is an extremely difficult course which we recommend only for highly skilled golfers.”
Birdie. A score on a hole which is one stroke less (better) than par (e.g., a 3 on a par-4 hole).
Birdie putt. A putt which, if made, would result in a birdie.
Bogey. A score on a hole which is one stroke more (worse) than par (e.g., a 5 on a par-4 hole). Originally, bogey and par referred to the same score, which is the score that would be achieved by an unbeatable “Bogey man.” By 1900 or so, improvements in equipment had made the old bogey standard obsolete for good golfers, and a new “par” was set.
Break of putt. From the golfer’s perspective, the left/right curving of a putt. An important part of reading a putt is determining how much break to play—that is, how far to the left or right of the hole to aim so that the ball breaks into the hole.
British Open. One of the four major championships in men’s professional golf. Played on a variety of courses in England and Scotland, it is the oldest of the major championships. The official name of the tournament is The Open Championship.
Brownian motion. A mathematical process that models the motion of a light particle being constantly bombarded by random forces.
Bump-and-run. A chip shot that is “bumped” a short distance in the air, lands short of the green, and rolls (runs) a long distance to the hole.
Bunker. A cavity in the ground, usually filled with sand (aka “sand trap”).
Caddie. A person who carries a player’s bag, and often gives advice. The word derives from the French cadet, or boy. Mary Stuart, Queen of Scotland and an avid golfer, is given credit for applying the name to golf.
Cane. A score of 7 on a hole.
Captain’s choice. A popular format for casual tournaments. On each hole, each player in the group (usually a foursome) hits a tee shot, the group captain chooses the best tee shot, all other balls are picked up, and everybody hits from the location of the best shot. The best of the second shots is chosen, and the process continues until the ball is holed out. Also called a “scramble.”
Carry. The distance that a ball travels from starting point to initial landing point (first bounce).
Chip. One type of shot from just off the green, usually played with a short swing, in which the ball pops into the air and then rolls along the green toward the hole.
Club difference. The change in number of iron used due to adjustments to terrain, wind, or other conditions. For example, if a golfer is at a distance from the hole where a 7-iron would normally be the correct club choice, a 2-club difference due to the green being at the top of a hill would make a 5-iron the correct choice. Since golfers typically have a 10-yard gap between irons, other ways to express this 2-club difference are “take two clubs more” and “the shot plays 20 yards longer.”
COR. Coefficient of restitution, a measure of the liveliness of a ball. Officially, COR equals the speed of the ball immediately after contact divided by the speed of the ball immediately before contact. If no energy is lost, COR = 1. If the ball is mush and loses all of its speed, COR = 0.
Correlation. A statistic that measures the extent to which two sets of data can be related by a first degree polynomial (line). A correlation of 1 or –1 means that one variable can be exactly obtained by substituting the other variable into an appropriate equation of the form y = mx + b.
Course rating. The score that a scratch golfer should average on a course. Course ratings are used to determine handicaps.
Cut. The process by which the large group of golfers that play the first few rounds of a tournament is reduced to a smaller group to play the last round(s) of the tournament. A typical PGA tournament starts with 132, 144, or 156 players for the first two rounds. The field is then cut to the top 70 golfers plus ties for the last two rounds.
Dimples. The indentations on a golf ball. Dimple patterns are symmetric but vary from ball to ball. (Some illegal balls have been designed with asymmetric dimple patterns, which cause the ball to rotate around a specified axis and can reduce hooks and slices.) The number of dimples also varies from ball to ball, although 336 is a common number.
Double bogey. A score on a hole that is two strokes more (worse) than par (e.g., a 6 on a par-4 hole). The amount over par is twice that of a bogey. If you “double” a hole, you make a double bogey.
Double eagle. A score on a hole that is three strokes less (better) than par (e.g., a 2 on a par-5 hole). This is also called an “albatross” (bigger than an eagle). Reportedly, Gene Sarazen referred to his famous 1935 double eagle at the Masters as a “dodo,” a very rare bird.
Downhill shot. A shot that travels from a starting point that is at a higher elevation than the landing point. A downhill lie indicates that the ground near the ball slopes downhill as you move a few feet toward the hole.
Drag force. A force that opposes the motion of a moving object, with a direction that is exactly opposite that of the object’s motion and depends on the speed of the object.
Draw. A long shot that curves slightly in a hook direction (right-to-left for right-handed golfers, left-to-right for left-handed golfers).
Drive. A tee shot hit with a driver. Sometimes the term refers to a long tee shot hit with a club other than a driver.
Driver. The longest and biggest club, used to hit the longest shots. The clubheads of drivers are generally large (460 cc) and are now molded in a variety of shapes. The driver is one of several clubs referred to as “woods,” an anachronistic term referring to the fact that the clubheads were made primarily of wood until the 1980s.
Driving range. A large, wide-open area for players to hit practice shots of all types.
Eagle. A score on a hole that is two strokes less (better) than par (e.g., a 2 on a par-4 hole). An eagle is a large bird, so we were spared the name “double birdie.”
Equilibrium value. A value of a variable in an equation which represents a constant solution; if that value is ever reached, the variable retains that value, as the forces that would change the value are balanced.
Expected value. The mean (average value) of a random variable, so that in some sense this is the value that you would expect to see.
Face angle. As viewed from above, the angle (in a horizontal plane) between a line from the ball to the target and a line from the ball that is perpendicular to the club face at impact. A nonzero angle typically results in a shot that is offline and/or curves.
Fade. A long shot that curves slightly in a slice direction (left-to-right for right-handed golfers, right-to-left for left-handed golfers).
Fairway. A stretch of well-mowed grass, usually connecting the tee area to the green, which is a preferred landing area for shots that are not expected to reach the green. In the fairway, you usually have a good lie for your next shot.
Fairways hit. The number of times a tee shot, excluding par-3 holes, finishes in the fairway (as opposed to the rough). The same term is used as shorthand for the fraction or percentage of times the golfer hits the fairway.
FedEx Cup. A year-long, points-based competition on the PGA Tour. The FedEx Cup playoffs consist of four tournaments, culminating in the Tour Championship.
Firm putt. A putt which is still moving at a high speed when it reaches the hole. If the putt is too firm, it might lip out.
Flop shot. A short shot taken from near the green with a very long swing and lofted club. The ball goes almost straight up in the air and lands with very little horizontal speed.
Fringe. A small area around the green that is less closely mowed than the green but more closely mowed than the fairway.
Front nine. The first nine holes on a golf course. This is followed by the “back nine” to make a round of 18 holes.
Frozen rope. A shot whose trajectory is so straight (and usually close to the ground) that it resembles a rigid rope.
Gallery. The group of spectators watching a tournament.
Game theory. A mathematical field in which “games” of competition are analyzed to determine optimal strategies. Generally, each player in the game has a set of strategies from which to choose. Each player simultaneously chooses a strategy, and the set of choices determines the outcome (payoff) of that round of the game.
Go low. Shoot a low (good) score for a round.
Going for the green. Trying to reach the green with a shot. When faced with a long shot over water, the golfer must decide whether to go for the green (try to hit over the water) or lay up (hit a shot that will stop before reaching the water).
Green. A closely mowed portion of the course around each pin (hole). On a green, you normally putt the ball and let it roll toward the hole.
Greens hit in regulation. The number of times, during a round, that a golfer reaches a green in the regulation number of shots. The regulation number, always two lower than the par on the hole, is the number of times a good golfer should hit the ball to get it on the green.
Gutta-percha ball. A ball made of gutta-percha, an inelastic latex produced from the sap of gutta-percha trees. Gutta-percha balls were used in the late 1800s and early 1900s and typically were scored to provide some of the aerodynamic benefits given by dimples. The more modern balata ball is made from a material that is very similar to gutta-percha.
Halve a hole. To tie a hole by making the same score as your opponent.
Handicap. A number assigned to a golfer to indicate how many strokes worse the golfer is than a scratch golfer. A golfer who has a handicap of 10 (a 10-handicapper) and shoots a 78 would have a net 68, which could be (more or less) fairly compared to the net score of some other golfer to determine the winner of a bet or a tournament.
Hazard. A feature of a golf course, typically to be avoided, in which some actions of a golfer are restricted (e.g., the golfer cannot ground the club— let the club touch the ground before the swing). Common hazards are water hazards and bunkers (sand traps).
Hickory sticks. An early style of golf club (becoming obsolete in the 1930s) in which the shaft of the club is made from hickory wood. Hickory shafts gave way to steel shafts, and graphite and other composite materials are used today.
High side. From the golfer’s perspective, the half of the green (either to the left of the hole or to the right) that has higher elevation near the hole. To make a putt, the golfer aims some amount to the high side and lets the putt break down to the hole. If you miss a putt on the high side, you played too much break (aimed too far away from the hole) for the speed of the putt.
Hole. (a) The cylindrical hole in the ground into which the ball must eventually be hit. (b) One of 18 layouts on a course, starting on a tee box and ending on a green. (c) A verb meaning that a shot goes into the hole; when you “hole out,” your ball goes into the hole and you have finished the hole.
Hook. A long shot that curves significantly from right-to-left for right-handed golfers or left-to-right for left-handed golfers.
Hybrid. A type of club that is designed as a cross between traditional woods and irons.
Intermediate rough. A strip of grass parallel to the fairway which is mowed lower than the rough but not as low as the fairway.
Iron. One of several numbered clubs with a thin, grooved face. The numbers relate to the length of the shaft and the loft of the face. The higher the number, the shorter the shaft and the more lofted the face; both differences cause shots with high-numbered irons (called short irons) to travel less horizontal distance than shots with low-numbered irons (called long irons). Irons range from a 1-iron (mostly obsolete) to a 9-iron and various wedges.
Iron shot. A shot using an iron.
Jab. A putting stroke that is an abrupt stab at the ball instead of a smooth backswing and long follow-through.
Lag putt. A putt, usually from a relatively long distance, in which the primary goal is to have the ball stop close to the hole. This usage is similar to that used in pool.
Laying up. A strategy in which the golfer does not go for maximum distance but chooses to hit the ball to an advantageous location. Instead of trying to hit a long shot over water, you might choose to lay up to a spot just short of the water.
Lie. The quality of the ball’s position on the ground. If you have a good lie, the ball is sitting up nicely on a smooth, flat patch of well-mowed grass. A bad lie can result from the surrounding grass being too long, or from there not being any grass around, or from the surrounding grass being sloped significantly in some direction, or other irregularities in the way the ball is positioned.
Lift force. A more common, less precise term that can refer to a Magnus force, usually used when the Magnus force has an upward component.
Line of putt. The direction in which a putt should start to enable it to go into the hole.
Lip. The edge of the hole.
Lip-out. A putt in which the ball hits a portion of the hole but catches the edge and bounces or spins away from the hole.
Loft of club. The angle between the plane of the clubface and a plane perpendicular to the ground. Common lofts range from 7° or 8° for some drivers to 60° or more for lob wedges.
Long iron. An iron that has a long shaft and is used to hit a long distance; 3-, 4-, and 5-irons are usually considered long irons.
LPGA. The Ladies Professional Golf Association.
Lumpy green. A green that looks smooth but has imperceptible indentations where people have stepped and the grass has not sprung back completely. These “footprints” can change the path of a putt.
Magnus force. The force resulting from the rotation of a moving object, which causes an asymmetry in the flow of air around the object. If the spinning object causes the air to deflect in one direction, there is an equal and opposite force that deflects the ball, causing its path to curve.
Make zone. An image showing the range of values of some variables corresponding to a made putt. One type of make zone shows the stopping points for made putts (if the hole had not been there). A different type of make zone shows combinations of initial speed and initial line for made putts.
Making the cut. Playing well enough in the first few rounds of a tournament to qualify for the last round(s) of the tournament.
Masters. One of the four major championships in men’s professional golf. It is always played at Augusta National Golf Club in Georgia the first week of April. Started by the great Bob Jones, it is a “tradition unlike any other.”
Match play. A 2-person or 2-team competition in which each hole is a separate contest. The winner of match play is the person or team that wins the most holes. The result of a match is described in terms of when the match ended. For example, if one person leads by four holes (has won four more holes than the other person) and there are only three holes left, then there is no need to play any further, and the winner takes the match 4 and 3.
Mean. One of several statistical averages of a collection of data or random variable. If there is a finite number of data points, the mean is the familiar sum of the values divided by the number of data points.
Medalist. The person with the best score in a one-round tournament. For this reason, stroke play is sometimes called “medal play.”
Missed green. A situation where the golfer is not on the green after taking the regulation number of strokes for that hole.
Modeling. A mathematical construction that is intended to capture in mathematical terms the most important aspects of some real-world situation.
MOI. Moment of inertia, a measure of the resistance to rotation for a particular object about a particular axis. The higher the MOI, the more resistance there is to changes in rotation rate. A club with a high MOI for the appropriate axis will rotate (twist) less for an off-center hit.
19th hole. Since a round consists of 18 holes, the 19th hole is a “watering hole” to sit down, talk, eat, and drink.
Off-line. A shot that does not finish on the line between the golfer and the hole.
One more club. A change of (typically) irons to a number that is one smaller. For example, if you cannot hit an 8-iron far enough to reach the green, you might need to take “one more club” (a 7-iron) to get the extra distance needed.
One-putt. Making your first putt on a hole.
Open clubface. Having the clubface “point” off-line in a particular way; that is, the line perpendicular to the clubface does not lie in the vertical plane containing the golfer and the target. For a right-handed golfer, an open clubface points to the right of the target (and a closed clubface points to the left of the target). For a left-handed golfer, an open clubface points to the left of the target (and a closed clubface points to the right of the target).
Par. A standard score for a hole. Par consists of the regulation number of shots, the number a good golfer should take to get to the green, plus 2 putts. For a professional golfer on an easy course, matching par is not good, and a round that is average (“par for the course”) might be several strokes under par. For a casual golfer, par is an exacting standard that is only occasionally met, and an average round is much worse than par.
Par save. A situation in which the golfer does not hit the green in regulation (misses the green) but makes a par nonetheless. It can also refer to a lengthy putt made to save par.
pdf. A probability density function. A function that contains all information about the probabilities of a random variable assuming different values. For a continuous pdf, the area under the curve from a to b is the probability that the variable assumes a value between a and b.
Penalty stroke. Under some circumstances, the golfer must add a stroke (the penalty stroke) as part of the process of resuming play on a hole. After hitting a ball into water, the golfer usually drops a new ball in a location designated by rule and also adds a stroke to the running score. For a lost ball or a ball hit out of bounds, you lose “stroke and distance,” meaning that you add a penalty stroke and hit the next shot from the original location.
Perimeter weighting. A style of clubmaking in which extra weight is manufactured into the edge of the clubface of an iron, resulting in an increased MOI.
PGA Championship. One of the four major championships in men’s professional golf. Played on a variety of courses in the United States, it is run by the Professional Golfers of America (which is different than the PGA Tour).
PGA Tour. The organization that runs most of the events played in the United States. It is distinct from the PGA and the USGA. Most of the golfers you watch in tournaments belong to the PGA Tour, whereas the pro at your local course probably belongs to the PGA.
Pin. Sometimes synonymous with “hole,” the pin is the pole stuck into the hole, usually with a flag at the top. A shot that is online is going “at the hole” or “at the pin” or “at the flag.”
Pitch. One type of shot from just off the green, usually played with a highly lofted club, in which the ball is hit high into the air and has a small amount of roll after landing on the green.
Pitch out. A short shot hit when the golfer is unable to make good progress to the hole, due to a tree in the way or high rough or other circumstance. Even though it feels like wasting a stroke, you pitch out (“take your medicine”) to a location from which you can hit a good shot.
Polar coordinates. A mathematical system of describing two-dimensional points by measuring the distance from the point to the “origin” (a special fixed point) and the angle counterclockwise from the positive x-axis to the line segment connecting the point and origin.
Pro-Am day. A day, usually the day before a tournament starts, in which the pros play with amateur partners of varying ability.
Pull. A shot which starts off heading to the left of the target for a right-hander or to the right of the target for a left-hander.
Push. A shot which starts off heading to the right of the target for a right-hander or to the left of the target for a left-hander.
Putt. For the purpose of official statistics, a putt is a shot taken from on the green. Typically, a putter is used to roll the ball along the green. A shot from off the green using a putter is not considered a putt.
p-value. When referring to a simulation of a golf round using G. H. Hardy’s rules, p is the probability of a given shot being excellent and also the probability of that shot being bad.
Q-school. The PGA Tour Qualifying Tournament. The top 125 money winners from one season automatically qualify as regulars for the following season. A multi-stage qualification process for players outside the top 125 culminates in a 6-round tournament in which approximately 150 players compete for 25 spots as regulars on the PGA Tour. These players are said to “earn their PGA card.”
Random variable. A mathematical function whose values are subject to randomness, although the distribution of values may be known.
Random walk. A mathematical sequence in which the next value is either one more or one less than the previous value, each with probability one-half. A physical realization of a random walk is a person who with each step wobbles randomly to the left or the right.
Range finder. A device that computes the distance from a golfer to a given feature, such as a pin or water hazard.
Read the green. To determine how the ball is going to roll on a green, specifically to know how hard and in what direction to hit a putt.
Regression to the mean. A statistical phenomenon in which extreme values of a random variable are followed by values that are closer to the mean.
Rough. The portion of a golf hole to either side of the fairway which consists of long grass and other vegetation that is not golfer-friendly. In the ShotLink system, “rough” is a broader designation meaning “not in the fairway” and includes trees and hardpan (hard, compacted ground).
Round of golf. Playing the 18 holes on a golf course.
Ryder Cup. A semi-annual competition between the United States and Europe, featuring hotly contested matches between many of the world’s best players in best ball, alternate shot, and match play singles formats.
Saving par. Making a par in spite of having missed the green or making a long putt for par.
Scrambling. In general, the expression refers to hitting good recovery shots such as bunker shots, chips from off the green, shots between and around trees, or long putts. The official statistic equals the fraction of time that a player misses a green and makes par or better.
Scratch golfer. A golfer with a 0 handicap. The origin of the term is related to the phrase “made from scratch” which indicates no head start or handicap.
Short. A shot which, from the golfer’s perspective, does not go as far as the hole.
Short iron. An iron for hitting short shots, short in length but with a high number, such as a 9-iron or wedge.
ShotLink. A system of lasers and volunteers run by the PGA Tour to collect data on the location and outcome of every shot in every round.
Side door. From the golfer’s perspective, the left or right edge of the hole.
Sidehill putt. A putt which will not, due to the slope of the green, roll directly toward the hole.
Skins. A multiplayer competition in which the golfer with the best score on a hole wins the bet (the “skin”).
Slice. A long shot that curves significantly from left-to-right for right-handed golfers or right-to-left for left-handed golfers.
Slope rating. A number assigned to each course to indicate how hard it plays for non-expert golfers and used in the USGA handicap system. An average slope rating is 113, and higher ratings indicate courses that play significantly harder than average for casual golfers.
Slow green. A green on which a rolling ball stops quickly, due to the length or the type of the grass. A slow putt can be due to a slow green, putting against the grain of the grass, or putting uphill.
Snowman. A score of 8 on a hole.
Spike marks. Golf shoes have spikes of different types to keep the golfer’s feet from slipping during the swing. Sometimes these spikes, especially pointed metal spikes, pull up portions of dirt or grass as they exit the ground. Spike marks can deflect a putt significantly but by rule may not be smoothed down by a golfer who is about to putt.
Spin the ball. To impart a lot of spin to the ball on a shot. With enough spin, the ball will not bounce or roll forward very much after landing.
Standard deviation. A statistical measure of the magnitude of the differences among values of a data set or random variable; in other words, it measures the dispersion or spread of values from the mean.
Standard error. A statistical estimate of the standard deviation based on a set of measurements.
Stimp meter. A ramp used to measure the speed of a green. The Stimp reading is how far in feet a ball rolls after leaving the ramp.
Stroke play. A type of competition in which the player with the fewest total strokes for the round wins.
Stymie rule. In singles match play until 1952, balls were not marked on the green unless they were within six inches of each other. If an opponent’s ball was in between your ball and the hole, you were “stymied” and could either try to putt around the ball or try to chip over it.
Swing angle. As viewed from above, the angle (in a horizontal plane) between a line from the ball to the target and the (tangent) line of the clubhead’s path near impact. A nonzero angle typically results in a shot that is off-line and/or curves.
Swing plane. The plane containing the rotating lines from clubshaft to club-head near contact. For most golfers, there is a different plane formed by the backswing. The intersection of the swing plane and a horizontal plane gives the line used to measure swing angle.
Swing speed. The speed of the clubhead at impact. This has been measured to be about twice the speed of the golfer’s hands at impact. Casual golfers have swing speeds in the 75- to 95-mph range, pros are in the 115- to 130-mph range, and long drive champions regularly reach 150 mph.
Tee shot. The first shot on a hole, usually with the ball sitting on a tee.
Three-putt. Needing three putts to get the ball in the stupid hole.
Trajectory. The path followed by a struck ball.
U.S. Open. One of the four major championships in men’s professional golf. Played on a variety of courses in the United States, it is run by the United States Golf Association.
Under par. Having a score that is less (better) than par. A golfer who is currently “3 under” (written –3) has taken 3 fewer strokes than the pars for the holes that have been played.
Up-and-down. From a location off the green, needing only one shot (up on the green) plus one putt (down into the hole) to finish the hole.
Uphill shot. A shot that travels from a starting point that is at a lower elevation than the landing point. An uphill lie indicates that the ground near the ball slopes uphill as you move a few feet toward the hole.
Vector. A mathematical entity that has both size (magnitude) and direction.
Wedge. One of several clubs that have large lofts and are used to hit high, short shots. Common wedges are pitching wedges (loft around 48°), gap wedges (about 52°), sand wedges (about 56°, with special “bounce” properties to help hit good shots from sand), and lob wedges (about 60°).
White tees. On a hole with several locations for tee shots, the white tee is the tee location that is used by average golfers. On some holes, there can be 50–100 yards’ difference between the white tees and the back tees.
z-score. Also called a standard score, a z-score estimates the number of standard deviations that a value of a random variable is above or below its mean.