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

Example Sentences

Since geologists first identified the formation in 2002, the three kilometer wide crater and its surrounding ring of circular faults spanning about 20 km have sparked intense debate.

From Science Daily • Mar. 11, 2026

And then the second definition, or threshold, is that it needs to be at least 0.01 square kilometer.

From Slate • Dec. 19, 2025

Typically, the further into the crust you go, the temperature increases by about 20 °C for every kilometer of depth.

From Science Daily • Oct. 16, 2025

Given the airline’s operating fleet remains at 78 aircraft as of October, the brokerage sees limited scope for any meaningful growth in Thai Airways’ average seat kilometer beyond a low single-digit percentage in 2H.

From The Wall Street Journal • Oct. 9, 2025

I felt bad to desert them all, but bonobos don’t range more than a kilometer a day, and Otto and I needed to go much faster than that.

From "Endangered" by Eliot Schrefer