The triathlon is a sport that includes three events, usually swimming, bicycling, and running. Athletes compete in triathlon at the summer Olympics every four years.
If you're an accomplished cyclist and runner, all you need to do is work on your swimming skills to enter a triathlon. You also need endurance; triathletes typically swim for 1500 meters, ride a bike for 40 kilometers, and then run a 10K. The person who completes all three sections of the triathlon in the shortest amount of time is the winner. This word was coined in 1970 from the prefix tri-, or "three," and the Greek athlon, "contest."