# millimeter

/ˈmɪɫəˌmitɝ/ (US) · CEFR A2 · Noun

Source: https://englishreference.com/word/millimeter
Updated: 2026-05-08

## Definition

a very small unit of length. There are ten of these in one centimeter and one thousand in a meter.

For teachers: a metric unit of length equal to one thousandth of a meter. Often used for precise measurements in technical or scientific contexts.

## Examples

- The insect is only one millimeter long.
- The carpenter measured the gap carefully to ensure it was within a millimeter of the plan.
- Modern manufacturing requires components to be machined with a tolerance of less than a millimeter to ensure the mechanical parts fit together perfectly.

## Pitfalls

- Not "ten millimeter" but "ten millimeters" — When used as a noun with a number greater than one, it must be plural; the singular form is only used when it acts as a modifier before another noun.

## Usage notes

- Commonly abbreviated as 'mm' in both technical and everyday writing.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.