"Scissor" kick: A propelling motion of the legs by which they move essentially like the blades of a pair of scissors, once used in competitive racing but now relegated to the sidestroke.

   Backstroke: A stroke in which the swimmer is on his or her back performing a flutter-kick and rotating the arms alternately backward.

   Breaststroke: A stroke made in the prone position in which both hands move simultaneously forward, outward and rearward from in front of the chest, and the legs move in a frog-like manner.

   Butterfly: A stroke made in the prone position where both arms are lifted simultaneously out of the water and flung forward, in combination with the dolphin kick.

   Crawl: A stroke made in the prone position characterised by alternate over arm movements and a continuous up-and-down kick; originally known as the Australian crawl.

   Dolphin kick: A kick performed in the butterfly stroke by which the legs are held together and moved up and down by bending and straightening them at the knee twice in quick succession; also used in backstroke starts and turns.

   False start: A start in which one or more swimmers leaves the blocks before the starting signal.

   False-start rope: A rope dropped into the water about 15 metres from the starting end of the pool to stop any swimmer who does not hear a false-start signal.

   Flutter-kick: A kick, usually performed as part of the crawl, where the legs are held straight and moved up and down alternately.

   Freestyle: An event where the swimmers may use any stroke they choose, which typically is the crawl.

   Gravity wave: The wave action, caused by the swimmers' bodies moving through the water, which moves down and forward from the swimmer, bounces off the bottom of the pool, then returns to the surface as turbulence.

   Heat: An early race in an event which qualifies the fastest finishers for the semi-finals or final.

   Lane: The area of the pool where each swimmer competes during a race.

   Lane lines: The dividers used to delineate the individual lanes, now constructed to dissipate surface turbulence.

   Lap: A length of the pool.

   Leg: One of a number of sections of an event or relay, each of which must be completed to determine the winner.

   Length: One lap; from one end of the pool to the other.

   Medley: A combination event in which a swimmer or relay team swims separate legs of backstroke, breaststroke, butterfly and freestyle.

   Negative split: A race strategy in which a swimmer covers the second half of a race faster than the first half.

   One start rule: A rule by which swimmers are disqualified after having caused a false start in an event.

   Relay: A race between teams of swimmers, with each swimmer swimming one leg of the event.

   Relay take-over: The exchange between the swimmer in the water and the next swimmer on the relay team.

   Roll: To move on the blocks before a team-mate touches the touch pad in a relay race to get a good start, legal as long as the swimmer doesn't leave the blocks before the team-mate has touched.

   Split: A swimmer's intermediate time in a race, registered every 50 metres, to record the swimmer's pace.

   Surf: To swim just behind a swimmer in an adjacent lane to take advantage of the wave created by that swimmer.

   Touch: To touch the end of the pool with the hand or hands, completing an event or relay leg.

   Tumble turn: An underwater roll at the end of a lap, used in backstroke and freestyle, allowing the swimmer to push off from the end of the pool with the feet.

   Turn: The turnaround by a swimmer at each end of the pool.

   Turn judge: An official at each end of the lane responsible for ensuring a swimmer turns correctly and, in the longer races, for displaying lap cards to inform a swimmer how many laps remain.

Credit: IOC

For further info., please visit http://www.olympic.org/uk/sports/programme/disciplines_uk.asp?DiscCode=SW.