A "half marathon" is a long-distance running event that covers a distance of 13.1 miles or 21.097 kilometers. Alternative terms that can be used for a half marathon include "21K," "half marathoner," "halfer," "split marathon," and "mini marathon." Some countries, like Japan and South Korea, use the term "half marathon" interchangeably with "half road-race." Other similar events include the "10K" and "5K" races, which cover distances of 6.2 miles and 3.1 miles, respectively. Additionally, there are ultra-running events that cover distances greater than a marathon, such as a 50K, 100K, and 100-mile races. Whatever the distance, these events test the physical and mental endurance of runners and draw crowds of enthusiasts and spectators alike.