Since 1983, the Meter has officially been defined as the length of the path traveled by the light in a vacuum during a certain time interval. The idea of a unified system of measures was first implemented in France at the time of the French Revolution. In the year 1789 a request was made to the members of the Academy of Sciences of that nation to create a unified system of measures. This system had several advantages compared to the previous ones, since the measures ceased to depend on parts of the human body, as they were until then, thus ceasing to be so arbitrary. This system was later followed by most countries in the world. According to the International System of Measures, the meter is considered to be the main unit of length measurement.
The word Kilometer is a combination of the prefix "kilo" (meaning thousand) with the word meter. That is the reason why one kilometer equals exactly one thousand meters. In spite of this, it should be noted that the abbreviation for the word kilometer is "km". To finish, never place the plural in the kilometer symbol, that is, whether it is 1 km or 8 km, the abbreviation should always appear in the singular.