millimeter

American  

[mil-uh-mee-ter] / ˈmɪl əˌmi tər /

especially British, millimetre

noun

• millimeters
  plural

1. a unit of length equal to one thousandth of a meter and equivalent to 0.03937 inch. mm

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millimeter Scientific  

/ mĭl′ə-mē′tər /

1. A unit of length in the metric system equal to 0.001 meter.

2. See Table at measurement

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Other Word Forms

Derived Forms

• millimetric
  adjective

Inflected Forms

Nouns

• millimeters
  plural

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Etymology

Origin of millimeter

First recorded in 1800–10; from French millimètre; see milli-, meter ¹

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Explanation

A millimeter is a tiny unit of measurement. The thickness of a dime is a little more than a millimeter, and there are a thousand millimeters in a meter. If you're using metric units to measure the length of something, you'll be dealing in meters and variations on meters, including millimeters. Look at a ruler that includes centimeters, the units of metric measurement that are closest in length to inches. The smallest units marked on the ruler are millimeters — there are ten of them in each centimeter. Although the word millimeter sounds like "million," it actually means "thousandth of a meter."

Example Sentences

See Examples For:

millimeter millimeters

They determined that a film measuring approximately half a millimeter offered an effective balance.

From Science Daily ● Oct. 23, 2026

Each bead measured only about half a millimeter across and contained a carefully controlled amount of silicon dioxide.

From Science Daily ● Sep. 12, 2026

They grow about a centimeter or two a year and by sampling cores at the millimeter scale, the team was able to develop windows of monthly temperature records scattered across the past millennium.

From Barron's ● Aug. 27, 2026

"That has paid off really well for us because there are a lot of people out there that are seeking that 70 millimeter presentation."

From Barron's ● Jul. 26, 2026

He came down with a nasty gash a millimeter above his right eye.

From "Seabiscuit: An American Legend" by Laura Hillenbrand

Despite differences among species and environments, the largest individuals tended to reach roughly 80 millimeters in the body measurement used by the researchers.

From Science Daily ● Oct. 16, 2026

They also had to be in direct contact -- a few millimeters apart, and nothing significant happened.

From Barron's ● Oct. 14, 2026

They were also able to inject different substances at separate depths, with delivery points spaced almost three millimeters apart.

From Science Daily ● Sep. 21, 2026

July’s 6.5 millimeters of rain in England, about 0.25 inches, was the lowest since records began in 1836 and less than half the next driest July—in 1911.

From The Wall Street Journal ● Aug. 31, 2026

His birthday at Alton Towers was canceled, Gavin Coley’s eyes sunk into his skull a few millimeters, and a year later his parents got divorced.

From "Black Swan Green" by David Mitchell

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