Definitions:
Biking
Stage - Any timed bike event of a given distance. A stage race may be more than one day.
Tour - An untimed bike event of a given distance. Usually a charity event (MS 100).
Velodrome - Any bike-track event.
Multi-Sport
Triathlon - Any race made up of 3 different sports but not limited to 3 segments or legs. (Swim-Run-Bike-Run)
Sprint
Swim = 1/2 mile or less
Bike = 10-15 miles
Run = 3-5 miles
Olympic
Swim = 1.5 K (.9 Mi.)
Bike = 40 K (24.8 Mi.)
Run = 10 K (6.2 Mi.)
Half Ironman
Swim = 1.2 miles
Bike = 56 miles
Run = 13 miles
Ironman
Swim = 2.4 miles
Bike = 112 miles
Run = 26.2 miles
Ultra - Any triathlon event longer than Ironman distance.
Off Road - Any triathlon event taking place on trails rather than roads. (The Xterra Series)
Duathlon - Any race made up of 2 different sports but not limited to 2 segments or legs. (Run-Bike-Run)
Short (Approx)
Run = 5 K (3.1 Mi.)
Bike = 20 K (12.4 Mi.)
Run = 5 K (3.1 Mi.)
Long (Approx)
Run = 10 K (6.2 Mi.)
Bike = 40 K (24.8 Mi.)
Run = 10 K (6.2 Mi.)
Biathlon - Winter biathlon events consist of Skiing and Shooting. Summer Biathlon events are running and shooting.
Adventure Racing - Endurance type events that include trail runs, hiking, climbing, canoeing repeling, etc. Some events are mulitple day.
