It is one of the Units of length within the SI (International System of Units), as one of the multiples of the meter, being equivalent to 1000 of them. Formerly, it was written with the letter "q" at the beginning, becoming kilometer; this is no longer in effect, but its use is still correct. It is part of the most used units; However, it was preceded by ancient metric systems, such as the foot (0.2957m), the elbow (41, 8 and 83, 87m), the league (between 4 to 7km) and the Stadium, a unit somewhat recognized, for having been one of the instruments for measuring the circumference of planet Earth, even if the total result was wrong by a few hundred kilometers.
The accepted symbol for kilometer is km which, unlike some, cannot be made plural or be considered an abbreviation of the original term. Nowadays, there are countries in which the kilometer is not used completely, as other units are already in use, such as the mile (0.621371192km), the nautical mile (0.539956803km) and the yards (1093.613298 km). Likewise, a kilometer contains approximately 1,000,000 millimeters, 100,000 centimeters, 10,000 decimeters, 1,000 meters, 100 decameters, and 10 hectometers.
Similarly, the kilometer can be squared and cubed, becoming km2 and km3. The first is based on a square that has a kilometer along all its sides, being mostly used in the measurement of hectares, since it is equivalent to 100 of them. The cubic kilometer contains 1 kilometer of side and, unlike the previous one, it is only suitable as a unit of volume.
