A kilometer is a unit of length in the metric system, equal to 1,000 meters. It is commonly used to measure distances, especially in countries that use the metric system. For example, road signs in many places indicate distances in kilometers, helping travelers understand how far they need to go. The abbreviation for kilometer is km. This unit is part of the International System of Units (SI) and is widely used in scientific contexts as well. One kilometer is approximately 0.621 miles, making it useful for converting distances between metric and imperial systems.