mmm

IPA/ˌɛmˌɛmˈɛm/
IPA/ˌɛmˌɛmˈɛm/

mmm — abbreviation

1. a written short form of 'micromillimeter' — a unit of length equal to one millio

1.abbreviationC1
Definition

a written short form of 'micromillimeter' — a unit of length equal to one millionth (1/1,000,000) of a meter, used in science and engineering to describe very small distances, sizes, or gaps.

Example

The coating on the lens was only 200 mmm thick, invisible to the naked eye.

number + mmm + adjective complement

Niran measured the diameter of the fiber at 35 mmm using an electron microscope.

scientific measurement context

Common collocations
  • mmm thick
  • mmm wide
  • mmm in diameter
  • below … mmm
  • within … mmm
Synonyms
  • µm

    the more common international symbol for micrometer/micron, equivalent to 1 mmm

  • micron

    an older term for the same unit; still used in some scientific fields

Grammar Patterns

number + mmm + (optional noun)

Usage Note

Always written in lowercase. Used almost exclusively in technical or scientific writing — you will rarely encounter 'mmm' in everyday speech or general media. Do not confuse with 'mm' (millimeter), which is 1,000 times larger.

Common Mistakes

The screw was 5 mmm long.
The screw was 5 mm long.
a 5-micromillimeter screw would be far too small for everyday use; 'mm' (millimeter) is the correct unit for visible objects.

Word family

  • micromillimeter
    nounC2
  • micrometer
    nounC1

Synonym discussion

Sense: abbreviation/1

All three refer to the same length (one millionth of a meter), but they differ in style and context. 'mmm' is the rarest form — you will see it mainly in older or specialized engineering documents where the writer spells out 'micromillimeter.' 'µm' is the modern SI (International System of Units) symbol and dominates scientific journal articles, lab reports, and measurement instruments. 'micron' is an older, non-SI name that remains common in biology (e.g., bacterial cell size), materials science, and manufacturing. For example, a biologist might say 'the bacterium is 2 microns long' but write '2 µm' in a paper. A mechanical engineer using a blueprint from the 1980s might encounter '50 mmm' as a tolerance.

mmm ↗µm ↗micron ↗

Common collocations

Nouns

Phrases

  • mmm in diameter
  • mmm thick
  • mmm wide

Prepositions

  • below … mmm
  • within … mmm
  • at … mmm

Etymology

GreekFrenchEnglish

'mmm' is formed by combining the SI prefix 'micro-' (from Greek 'mikros,' meaning 'small') with 'millimeter.' The triple-m abbreviation mirrors the structure of other metric units: just as 'mm' stands for 'millimeter,' 'mmm' adds the 'micro-' prefix to create 'micromillimeter.' It follows the same pattern as other metric abbreviations used in scientific writing.