The kilometre (American spelling: kilometer), symbol km is a unit of length in the metric system, equal to one thousand metres.

Slang terms for kilometre include click (sometimes spelled klick or klik) and kay (or k).

Pronunciation

There are two different pronunciations for the word:

• /ˈkɪl.əˌmiː.tə(r)/ and
• /kɪˈlɒm.ə.tə(r)/.

The former pronunciation follows the general pattern in English whereby metric units of measurement are pronounced with the stress on the first syllable, and preserves the correct pronunciation of metre. However, the latter pronunciation; which follows the stress pattern used for the names of measuring instruments (such as micrometer, barometer, thermometer, tachometer and speedometer); is in common usage. Kingsley Amis has suggested that this pronunciation (and the American spelling) be reserved for the thousand-measurer, the wall which Herodotus says Xerxes built around a thousand troops so he could count his army.

International usage

The United Kingdom and the United States are the only two developed countries which continue to use miles on road signs.Fact: date=August 2008

Although the UK has officially adopted the metric system, there is no intention to replace the mile on road signs in the near future, owing to the British public's attachment to traditional imperial units of distance, i.e., miles, yards and inches, and the cost of changing speed signs (which could not be replaced during general maintenance, like distance signs, for safety reasons). As of 11 September 2007, the EU has not challenged Britain's use of the imperial systems. EU commissioner Günter Verheugen said: "There is not now and never will be any requirement to drop imperial measurements."

In the US, the National Highway System Designation Act of 1995 prohibits the use of federal-aid highway funds to convert existing signs or purchase new signs with metric units. However, the Manual on Uniform Traffic Control Devices since 2000 published in both metric and American Customary Units. (See also Metrication in the United States.)

See also

• Conversion of units, for comparison with other units of length
• Cubic kilometre
• Orders of magnitude (length)
• SI prefix
• Square kilometre