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

"The millimeter and submillimeter radio bands remain almost completely unexplored for SETI, so this is really about opening up a new area of parameter space to search."

From Science Daily ● Jul. 30, 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

The cutting-edge 3-nanometer process can fit 250 million to 300 million transistors in one square millimeter of silicon.

From The Wall Street Journal ● Jul. 24, 2026

For a terrible moment, Woolf clung to Seabiscuit’s neck, a millimeter from falling off, then regained his balance.

From "Seabiscuit: An American Legend" by Laura Hillenbrand

The other five pairs were separated by gaps measuring only a few millimeters.

From Science Daily ● Oct. 19, 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

The Duo weighs 254 grams, and is 11.3 millimeters thick when closed.

From The Wall Street Journal ● Sep. 10, 2026

The film itself, loaded into the T-50 by specially trained technicians, was barely wider than the lens—a mere five millimeters.

From "Spies: The Secret Showdown Between America and Russia" by Marc Favreau

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