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A kilometer (km) is a unit of length in the metric system, equal to 1,000 meters.
The plural form is kilometers.
The term "kilometer" is composed of two parts: the metric unit "meter" and the Greek prefix "kilo," which comes from the word "khilioi," meaning "thousand."
Thus, a kilometer translates to one thousand meters.
This concept is a fundamental aspect of the decimal-based metric system, established in France during the 1790s. The logical, prefix-based nature of the metric system simplifies conversions, which is a key reason for its widespread adoption.
The kilometer is the official unit of measurement for geographical distance in the vast majority of countries worldwide.
Only a few nations still primarily use the mile for road signage and navigation, most notably:
For international travel, science, and sporting events like marathons and the Olympics, the kilometer is the universally accepted standard.
To understand how far a kilometer is, consider these real-world examples:
This consistent unit of measurement makes it easy to compare everything from everyday travel to distances in space.