What does micrometre mean?
A micrometre is a metric unit of length equal to one millionth of a metre. It is used in science, engineering, medicine, and manufacturing to describe dimensions too small to be measured conveniently in conventional units. In biology, for example, microorganisms and the structures within cells may be measured in micrometres, while precision engineering may specify tolerances or resolutions of a few micrometres. The word is most common in British English; American English generally spells it micrometer, while micron is also widely used in technical contexts. A micrometre should not be confused with a nanometre, which is one thousand times smaller, or with a millimetre, which is one thousand times larger. Although the unit is tiny by everyday standards, it occupies an important place in the metric system and makes very small measurements possible with clear, standardized units.
nounA micrometre is a metric unit of length equal to one millionth of a metre, or 0.000001 metre. It is used especially in science and technology for very small measurements.
- A unit of length equal to one millionth of a metre, used for measurements on a microscopic scale.
"The cell wall was only a few micrometres thick."
"The microscope can resolve structures less than one micrometre apart."
"The manufacturing tolerance was specified to within a few micrometres."
The standard British plural is micrometres; the American plural is micrometers.
"The fibres are only a few micrometres in diameter."
A micrometre is one millionth of a metre—and the diameter of a typical bacterium is often just a few micrometres.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of micrometre
Micrometre combines the combining form micro-, derived from Greek mikros, meaning “small,” with metre, from Greek metron, meaning “measure.” The prefix micro- was already established in scientific English for very small quantities and, within the metric system, denotes one millionth. The compound belongs to the nineteenth-century development of systematic metric terminology, in which prefixes derived from Greek were combined with standard units.
Related word forms
How micrometre is actually used
Micrometre is the British spelling; American English normally uses micrometer. The shortened form micron is especially common in American scientific and technical usage.
Easily confused with micrometre
Micrometer is the standard American spelling of the same metric unit; in British English, the word is written micrometre.