：

Km refers to the commonly used unit of length measurement, commonly known as km, abbreviated as km,1km =1000 m. It is usually used to measure the distance between two places. The unit of length refers to the basic unit for measuring spatial distance, which is formulated by human beings to standardize the length. Its international unit is meter, and commonly used units are millimeter, centimeter, decimeter, kilometer, meter, micron and nanometer. Length units play an important role in various fields.

Guide: Kilometers, commonly known as kilometers, are expressed in kilometers. 1790 in may, a special Committee composed of French scientists suggested that one fortieth of the total length of the earth meridian passing through Paris should be used as the unit of length.