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Kilometre

physical science Maturity 11-13 Next article →

A kilometre is a way to measure length.

Division of the meridien
Division of the meridien

It is part of the International System of Units, or SI. One kilometre is equal to one thousand metres. The prefix "kilo-" means one thousand. Most people use it to measure distances on land. This includes distances between different places. The United States and the United Kingdom are exceptions. They use the statute mile instead. The symbol for a kilometre is km.

There are two common ways to say the word. Some people put the stress on the first part. This sounds like the word kilogram. The BBC and ABC use this way. Other people stress the second part of the word. This sounds like the word thermometer. This way is used in many countries. It is different from how other SI units work. This happens because the stress pattern is irregular.

Long ago, France wanted a new way to measure. The French National Constituent Assembly ordered this in 1790. In 1793, they made the metre the main unit. They based it on the distance from the poles to the Equator. The first name for a kilometre was "Millaire." Later, people often used the myriametre instead. One myriametre is ten thousand metres.

Different places used different names for a long time. The Dutch used the kilometre in 1817. They called it a "mijl." In the Netherlands, it became the official unit in 1867. By 1842, the kilometre was used in Italy. In 1935, the myriametre was officially stopped. The International Committee for Weights and Measures abolished the prefix "myria-" then. This left the kilometre as the main unit.

We can compare a kilometre to many other things. One kilometre is about 0.621 miles. It is also about 540 nautical miles. You can even compare it to space measurements. It is much smaller than an astronomical unit. It is also smaller than a light-year or a parsec. In the US and UK militaries, soldiers use a slang term. They call a kilometre a "klick."

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