kilometer

American  

[ki-lom-i-ter, kil-uh-mee‑] / kɪˈlɒm ɪ tər, ˈkɪl əˌmi‑ /

especially British, kilometre

noun

1. a unit of length, the common measure of distances equal to 1,000 meters, and equivalent to 3280.8 feet or 0.621 mile. km

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kilometer Scientific  

/ kĭ-lŏm′ĭ-tər,kĭl′ə-mē′tər /

1. A unit of length in the metric system equal to 1,000 meters (0.62 mile).

2. See Table at measurement

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kilometer Cultural  

1. In the metric system, one thousand meters, or about five-eighths of a mile.

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Pronunciation

The usual pronunciation for units of measurement starting with kilo-, as kilocalorie, kiloliter, and kilohertz, as well as for units of length ending in the base word meter, as centimeter, hectometer, and millimeter, gives primary stress to the first syllable and secondary to the third. It would seem logical for kilometer to follow this pattern, and in fact the pronunciation has been used since the early 1800's. A second pronunciation: , with stress on the second syllable only, was first recorded in America before 1830. Although often criticized on the basis of analogy, this pronunciation has persisted in American English, increasing in frequency, and has gained popularity in British English as well. It is reinforced by words for instruments (rather than units) of measurement ending in -meter, as thermometer, barometer, and speedometer, having stress on the -om syllable. Both pronunciations are used by educated speakers, including members of the scientific community.

Other Word Forms

• kilometric adjective
• kilometrical adjective

Etymology

Origin of kilometer

First recorded in 1800–10; from French kilomètre; kilo-, meter ¹

Explanation

A kilometer is a unit of metric measurement that's about 2/3 as long as a mile. If you sign up for a five kilometer race, you'll be running a course that's a little over three miles long. Most countries around the world measure geographical distance using kilometers rather than miles — the exceptions are the U.S. and the U.K. The word means "one thousand meters," from Greek roots khilioi, "thousand," and metron, "measure." As you might guess, there are a thousand meters in a single kilometer. If you drive from the U.S. across the Canadian border, expect to see speed limit signs change from miles per hour to kilometers per hour.

Example Sentences

Over the course of two-and-a-half years, researchers found only one clear example of a raven following a wolf for more than one kilometer or more than an hour.

From Science Daily • Mar. 19, 2026

To identify detailed pollution patterns, the team divided the continental United States into a grid made up of 4 kilometer by 4 kilometer squares.

From Science Daily • Jan. 26, 2026

Once the glacier is either less than 0.01 square kilometer or less than 1 percent of its initial volume, you cannot call it a glacier anymore.

From Slate • Dec. 19, 2025

Also, the airline’s yields will probably decline to THB2.60 per revenue passenger kilometer in 3Q from THB2.66 in 2Q, partly because of intensified competition, the analyst adds.

From The Wall Street Journal • Oct. 9, 2025

But as we walked along, step after step, kilometer after kilometer, my stomach began to gnaw away at itself.

From "Prisoner B-3087" by Alan Gratz