IN 1896, swimming became an Olympic sport for men. And women’s swimming events became a normal part of the Olympic Games in 1912. Men and women now take part in 16 events each.
The program includes four different strokes（泳姿）across different distances. Freestyle（自由泳）races cover 50, 100, 200, 400, 800, 1500, and 10,000 meters. The 800m is for women only, and the 1500m for men only. The butterfly（蝶泳）, backstroke（仰泳）and breaststroke（蛙泳）races each cover 100 and 200 meters. All four strokes are used in the 200m and 400m individual medley events（个人混合泳项目）.The 4 × 100m freestyle, 4 × 200m freestyle and 4 × 100m medley relays（接力赛）complete the program.
Each race has eight swimmers at most. Preliminary heats（预赛）in the 50m, 100m and 200m lead to semi-finals（半决赛）and finals（决赛）according to the fastest finishing time. In relays and individual events of 400 meters or more, the eight fastest finishers in the preliminaries enter finals directly.
