Kilometr

Kilometr, also spelled kilometre or kilometer in different languages, is a unit of length equal to 1,000 metres. Its symbol is km. The kilometre is not a base SI unit but an SI-derived unit accepted for use with the SI; it is defined by the metre as 1,000 metres.

The name combines the prefix kilo- meaning thousand with metre. In English, variations include "kilometre" (British) and "kilometer" (American). In several languages, notably Polish, Czech and Slovak, the form "kilometr" is standard.

Kilometres are commonly used to express terrestrial distances, including road, rail, and geographic distances, as well as measurements on maps and in athletics for longer routes. They are also used in aviation to describe distances between airports, though nautical miles are common in seafaring contexts.

Conversion and usage: 1 kilometre equals 1,000 metres, and roughly 0.621371 miles. In speed units, 1 kilometre per hour equals about 0.27778 metres per second. The prefix kilo- indicates 10^3, so larger multiples follow the same pattern (for example, 10 kilometres = 10,000 metres). The kilometre remains a widely used unit for measuring longer distances in everyday life and science, particularly outside the United States.