Block: The starting platform; the area from which a swimmer dives into the pool to begin a race. 

Cap: Latex or lycra head covering used during a race or workout to protect a swimmer's hair from the effects of chlorine; also serves to eliminate drag from a swimmer's hair. 

Catch phase: The beginning part of the stroke where the arms and hands start to propel the body. 

Command: On the long whistle from the referee, swimmers step onto the starting platform or, in the case of the backstroke and medley relay races, enter the water. On the starter's command — "take your mark" — swimmers immediately take a starting position, with at least one foot at the front of the starting platform. When all swimmers are stationary, the starter gives the starting signal. 

Dolphin kick: Used in the butterfly, and during underwater portions of freestyle and backstroke races, where the thrust of the kick comes from the hips, and the feet and legs are held together. 

Drafting: A maneuver in which one swimmer is just behind another in an adjacent lane and uses the fast-moving water generated by their opponent to overtake the competitor. A memorable example of drafting is Jason Lezak's anchor leg in the men's 4x100m freestyle relay from the 2008 Beijing Games. 

Drag suit: A second, loose-fitting suit worn in workouts and warm-ups to add weight and resistance. The concept is similar to a baseball player swinging two or three bats in the on-deck circle. 

Exchange: Occurs during relays when one swimmer touches the wall and the next swimmer dives in. Relay exchanges are often where false starts occur, as swimmers on the blocks are looking for an edge and accidentally dive in before the previous swimmer touches the wall. A swimmer can leave the blocks up to .03 of a second before the previous swimmer touches the wall, but the team is disqualified if a swimmer leaves any time earlier than that. 

False start: Occurs when a swimmer either leaves the starting block or is moving on the block before the starter officially starts the race. Since 1998, there has been no warning false start. Any swimmer starting before the starting signal will be disqualified. If the starting signal sounds before the disqualification is declared, the race will continue, and the swimmer(s) will be disqualified upon completion of the race. 

FINA: The Federation Internationale de Natation is the world governing body for aquatic sports including swimming, diving, water polo, and artistic swimming. FINA sets qualifying standards and the rules for aquatic sports at the Games. 

Final: The last race of an event and the one in which medalists are determined. Typically, a final comprises the eight fastest swimmers from two preceding, semifinal races. 

Flags: Hanging flags placed above the pool five meters from each wall. They enable backstrokers to execute a turn more efficiently by providing a mark by which to count their strokes. 

Flat start: Refers to the start of a race, where the swimmer stands still on the blocks and waits for the starter's signal, as opposed to a relay start via an exchange. A flat start is considerably slower than a relay start. 

Flip turn: Used in freestyle and backstroke races, where swimmers somersault before reaching the wall and push off with their feet, never touching the wall with their hands. 

Goggles: Eyewear worn in the pool to protect swimmers' eyes from the effects of chlorine. In the past, swimmers used saliva or wiped a cigarette on the inside of their goggles to prevent them from fogging up mid-race. Today's goggles are fogless, fit better and even come with polarized lenses to cut down on outdoor glare. This innovation is particularly helpful to backstrokers, who used to go "sun blind" while swimming outdoors. 

Gravity wave: Wave action caused by the bodies moving through the water. Gravity waves move down and forward from the swimmer, bounce off the bottom of the pool and return to the surface in the form of turbulence. 

Gutter: The area at the edges of the pool into which water overflows during a race; the water is then re-circulated into the pool. Deep gutters catch surface waves and don't allow them to wash back into the pool and affect the race. 
 
Heat: A grouping of swimmers assembled to compete in a race. Most often used to refer to the individual races of the preliminary round of competition, though the term can apply to semifinals and finals as well.  
 
IM: Abbreviated term for individual medley, an event in which the swimmer uses all four competitive strokes in the following order: butterfly, backstroke, breaststroke, freestyle. 

Lane lines: The dividers used to create lanes. These are made of individual finned discs that are strung on a cable and rotate when hit by a wave. The rotating discs dissipate surface-tension waves in a competitive pool. 

Lap: One length of the pool. A 100m race (down and back) is two laps. 

Long course: A term used to describe a pool in which one length measures 50 meters. The Olympic Games are conducted at long-course venues. 

Negative split: A race strategy in which a competitor swims the second half faster than the first. 

Official: A judge on the deck of the pool. Various judges watch the swimmers' strokes, turns and finishes. Some officials are timers. 

Prelims: Short for preliminaries, which describes the round of races in which competitors try to qualify for the semifinals (or final, in events without semifinals). Also called heats. 

Pullout or pulldown: The beginning of a breaststroke start or turn, where a swimmer is allowed one long pull down to their waist, during which a single butterfly kick is permitted, followed by a breaststroke kick.   

Reaction time: The time it takes for a swimmer to leave the blocks after the starter gives the signal. Modern timing systems are equipped with sensors that mark the time elapsed, which is generally less than one second. In relays, reaction time for the second, third and fourth legs are measured from when the swimmer in the water touches the wall to when the next swimmer leaves the blocks. 

Recovery phase: The conclusion of the stroke where the hand and arms finish pulling and set up to start the next stroke cycle.  

Ready room: The staging area within the venue where swimmers in upcoming heats wait to swim. Some swimmers use this setting to socialize with competitors, while others try to use “mind games” to interrupt their opponents’ focus. 

Relay start: Refers to the second, third and fourth swimmers in a relay, where they dive in when the previous swimmer touches the wall. Relay starts are faster than flat starts, because swimmers can anticipate when they can dive in, and they are allowed to leave the blocks up to .03 seconds before the previous swimmer touches. 

Roll: To move on the starting blocks prior to the starting signal. A roll is usually caught by the starter and called a false start, but swimmers will often try to guess the starter's cadence and get a good start. Similar to a false start infraction in football. 

Scratch: To withdraw from an event in a competition. 

Shaving: To cut down on resistance and provide a feeling of slipperiness in water, a swimmer shaves his/her entire body before big meets. The physical effects are minor, but the mental factor often is enormous. 

Short course: A term used to describe a pool in which one length measures 25 meters (or 25 yards). Most college pools are short courses, and most events during the winter are held at short-course venues. The Olympics are held in long course (50m) pools. 

Split: The time registered by a swimmer when he or she finishes each length of the pool. Splits can be used to show which segment of a race a swimmer covered in noteworthy time, to indicate rank order after each 50m increment, and to convey whether a swimmer is matching a notable record's pace. Also, split can refer to the time a relay swimmer takes to complete his/her leg of the race. 

Sprint: Refers to short intense swims of usually not more than 100 meters. 

Taper: The gradual process of resting in preparation for competition. During the middle of the swimming season, a swimmer might work out 10,000 to 15,000 meters (8 to 10 miles) each day. As a major competition draws near, the swimmer will "taper" off the distances each day. A perfectly designed taper will enable the swimmer to compete at the peak of his/her ability. 

Touch: The finish of the race. 

Touchpad: The area at the end of each lane in the pool where a swimmer's time is registered and electronically sent to the timing system, which sends the time to the scoreboard. 

Track start: Position on the starting blocks where the swimmer places one foot at the front of the block and one foot farther back. 

Turnover: The number of times a swimmer's arms turn over (cycle) in a given distance or time during a race. 

Warm-down: Additional swimming or activity used by a swimmer to rid the body of excess lactic acid generated during a race. Also called "cool-down." 

Warm-up: Additional swimming or activity used by a swimmer in preparation shortly before a race.

Acclimate: To become accustomed to warmer or colder water temperatures and conditions before an open water race. 

Beeline: The most direct and straightest route to a specific point during a race, albeit not necessarily always the fastest route due to currents or waves. 

Boxed-in: To get caught in between swimmers so as to not be able to swim in the desired direction or pace. 

Breakaway: To speed up or increase the pace in order to create separation from the rest of the field. 

Corrected course: The most direct course to the next turn buoy accounting for drift due to actual or anticipated currents, wind and wave action. 

Course:  The path on which the race is swam, marked off by buoys in the water. 10k races often include multiple laps of the course. 

Current: A portion of a large body of water moving in a certain direction. A steady forward movement of water; the flow of a body of water, regardless of cause. The horizontal movement of water in a channel or bay. 

Cut buoy: In the case of a swimmer who did not properly round a required turn buoy, a violation of the rule that requires the swimmer to return and correctly round the turn mark. 

Dock: A fixed pier or floating platform where open water swimmers can either start or finish races or that serve as feeding stations or locations where supporters can cheer. 

Draft: To swim closely behind another swimmer(s) in order to take advantage of their slipstream, especially in a race. 

Escort: A person or group of persons in a boat, kayak, personal watercraft, or on a paddleboard or surfboard accompanying or leading a swimmer for protection and/or guidance in the open bodies of water. 

Feeding: The process of eating, drinking or being given nourishment during a race. 

Feeding station: A boat or other temporary or fixed floating structure, such as a dock or pier, used by coaches to provide food or drink to swimmers in a race. 

Feeding stick: Also called a feeding pole, a long slender mechanical instrument with a cup or bottle holder at the end, used to hand food or drink to a swimmer during a race. 

Finish chute: A series of lane lines, buoys or other such markings that indicate the finish area and help direct the swimmers to the final finish line or touch pads. 

Fluid: Liquid nourishment that provides hydration designed to restore or maintain fluid balance during an open water race. Popular examples are juice, rehydrating drinks and water. 

Gel pack: Small, easy-to-use, individual squeeze packages that contain simple and complex carbohydrates, antioxidants and amino acids in order to provide an energy boost during a race. Single-serving pouches are sold in a variety of sizes, shapes and flavors, and can be easily digested while swimming. 

Gulp and Go: When an open water swimmer quickly consumes fuel (e.g., gel pack) or hydration (e.g., water) received from his/her coach on the feeding pontoon, then immediately begins to swim again after the momentary feeding stop. 

Impede: To obstruct, interfere or slow in movement or progress by means of cutting off, swimming into, blocking or pulling on legs, ankles, arms or shoulders of other swimmers during a race. 

Intermediate buoy: Buoys placed between required turn buoys or markers that may be passed on either side without penalty. 

In-water start: A start that begins in the water and does not require swimmers to dive in from a starting dock or run in the water from a beach, pier or shoreline to start. 

In-water finish: A finish that is in the water and does not require the swimmers to exit from the body of water where the race is held. 

Lanolin: A greasy, fatty substance, insoluble in water, that is extracted from wool-bearing animals used to coat the skin of swimmers, especially on friction points (e.g., underarms, inside thighs, chin and neck) in order to prevent chafing or help reduce the impact of cold water. 

Lap: One complete round, length or circuit around a race course. 

Lead boat: A boat or similar watercraft that leads a swimmer or the lead pack of swimmers on a race course. 

Lead pack: The fastest or first group of swimmers in a race, all closely swimming together. 

Left (or right) shoulder turn: Term used by race officials to describe the required turn direction when passing a turn buoy. A left shoulder turn means that the turn buoys must be kept on the left-side of the swimmer. 

Line of sight: An unobstructed path from the swimmer's eye to a distant point such as the turn buoys or finish line. 

Marathon swimming: Swimming a minimum of 10 kilometers (6.2 miles) in the large outdoor bodies of water such as oceans, bays, lakes, reservoirs, rowing basins and rivers, as defined by FINA. Also called "open water swimming" or "the 10k." 

Marking: Numbers that are written in black on the shoulders, shoulder blades and wrists of the swimmers for identification purposes. These numbers are used to monitor the swimmer's progress, announce the swimmer's position to the crowd and media, and to inform swimmers who commit rule infractions during the race. Alternatively called race numbers. 

Positioning: A place or location, often strategic and intentional, but occasionally unintentional or accidental, where a swimmer finds him/herself during an open water race. 

Rabbit: A swimmer whose goal is chiefly to set a fast pace, either to set a record or to exhaust a specific competitor so that a teammate can win. 

Reach and Roll: When the swimmer extends his/her hand to grab fuel (e.g., gel pack) or hydration (e.g., water) from his/her coach on the feeding pontoon, then turns over on his/her back to consume the fuel or hydration. 

Red card: A red-colored penalty card that indicates the immediate disqualification of a swimmer due to unsportsmanlike conduct or a serious infraction of the rules during an open water race. 

Referee: The designated individuals who judge open water races based on the established rules set by FINA or the race director. Referees can be located at the start, turns, finishes and/or on escort boats along the course. 

Seek and Spot: During feeding, when the swimmer heads toward the feeding pontoon and identifies his/her coach standing on the pontoon. 

Slip streaming or drafting vessels: Intentionally taking advantage of the wake of escort boats or officiating watercraft on the course; rules prohibit this action by swimmers. 

Starting platform: A dock, pier or other floating structure where the swimmers stand to start an open water race; each swimmer is given about 60 centimeters of space on the starting platform. 

Stick and stay: To draft off another swimmer for an extended period during a race 

Strung out: To become separated from one another during an open water race, especially in the later stages of the race after the swimmers have been swimming together in a pack. 

10K: 6.2 miles or 10 kilometers, the standard distance of the Olympic open water swim. 

Toss and Turn: During feeding, when the swimmer quickly discards the fuel (e.g., gel pack) or hydration (e.g., water cup or bottle) received from his/her coach and immediately turns over on his/her stomach to begin swimming after a momentary feeding stop. 

Touch pad: Finish plates placed vertically (i.e., perpendicular to the surface of the water) at the end of open water races that identify the race finish and can be electronically tied to the official timing system. 

Turn buoy: A distinctively marked colored float in the water, anchored to mark the course for swimmers. 

Unsportsmanlike conduct: Inappropriate or unprofessional acts committed by swimmers during an open water race that are not in the spirit of the competition. These acts include obstruction, interference or making intentional contact with another swimmer, and can lead to a warning or disqualification by the lead referee, whether made by the swimmer or the swimmer's escort boat or crew. 

Wake: The track of waves left by an escort boat, personal watercraft or other watercraft moving through the water or across the path of swimmers in an open water race or solo swim. 

Yellow card: A yellow-colored penalty card that indicates an official warning to a swimmer due to unsportsmanlike conduct or an infraction of the rules during an open water race.