: a metric unit of length equal to 1000 meters see Metric System Table
How do you pronounce kilometer?: Usage Guide

In North American speech kilometer is most often pronounced with primary stress on the second syllable. This pronunciation is also heard frequently in British speech. Those who object to second syllable stress say that the first syllable should be stressed in accord with the stress patterns of centimeter, millimeter, etc. However, the pronunciation of kilometer does not parallel that of other metric compounds. From 1828 to 1841 Noah Webster indicated only second syllable stress, and his successor added a first syllable stress variant in the first Merriam-Webster dictionary of 1847. Thus, both pronunciations are venerable. Most scientists use second syllable stress, although first syllable stress seems to occur with a higher rate of frequency among scientists than among nonscientists.

Did you know?

A kilometer is equal to about 62/100 of a mile, and a mile is equal to about 1.61 kilometers. The U.S. has been slow to adopt metric measures, which are used almost everywhere else in the world. Though our car speedometers are often marked in both miles and kilometers, the U.S. and Great Britain are practically the only developed nations that still show miles rather than kilometers on their road signs. But even in the U.S., footraces are usually measured in meters or kilometers, like the Olympic races. Runners normally abbreviate kilometer to K: "a 5K race" (3.1 miles), "the 10K run" (6.2 miles), and so on.

Examples of kilometer in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The satellites orbit thousands of kilometers above the Earth, well above altitudes where wisps of atmosphere can perturb their orbits. Mary Randolph, Scientific American, 8 July 2026 One patch of material was over 4 kilometers long, and the researchers estimate the total amount of new material at about 150 million cubic meters. John Timmer, ArsTechnica, 8 July 2026 Iran has several missiles and drones in its inventory with enough range to make the roughly 800-mile (1,300-kilometer) flight from its own borders to Turkey, including some of its Shahed drones and Shahab ballistic missiles. ABC News, 8 July 2026 Opening the door of a plane in mid-air is extremely difficult, explained Álvarez, who compared it to trying to open the door of a car traveling at 200 kilometers an hour (124 miles per hour). Jack Guy, CNN Money, 8 July 2026 See All Example Sentences for kilometer

Word History

Etymology

French kilomètre, from kilo- + mètre meter

First Known Use

1810, in the meaning defined above

Time Traveler
The first known use of kilometer was in 1810

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Cite this Entry

“Kilometer.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/kilometer. Accessed 10 Jul. 2026.

Kids Definition

: a metric unit of length equal to 1000 meters see metric system

Medical Definition

kilometer

noun
ki·​lo·​me·​ter
: 1000 meters

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