micron

Etymology

According to the revised OED, it is borrowed from German Mikron, used by J. B. Listing in 1869,^[2] while Barnhart and Wiktionary derive it from French micron (1880),^[3][1] Etymonline describes it as coined in French,^[4] and Merriam-Webster and Collins call it New Latin micron.^[5][6][7] All trace it to Ancient Greek μικρόν (mikrón, “a small thing”), the neuter of μικρός (mikrós, “small”), the source of micro-.^{[2][8][3][9][1]}

Earliest recorded meaning

One millionth of a metre: the OED's first quotation is from the American Journal of Mathematics (1879), the year the International Committee for Weights and Measures adopted the term, with the symbol μ, for its publications.^[2][4] Merriam-Webster Unabridged also gives 1879,^[6] the 1989 edition of the OED 1880, Etymonline 1883 and Barnhart 1885.^[10][4][3]

Semantic evolution

The micron was used as a unit of length for very small things, a thousandth of a millimetre.^[6][2] In the International System of Units it was replaced by the micrometre in 1968,^[4][10] though Collins notes that the replacement is still under way.^[7] Merriam-Webster Unabridged also records it as a unit of low pressure, as in a vacuum tube.^[6] The plural is microns, or, less often, micra.^[6][7]

Timeline

• 1879 – one millionth of a metre, adopted by the International Committee for Weights and Measures.^[2][6][4]

Meanings

Noun

1. A unit of length equal to one millionth of a metre, or one thousandth of a millimetre; a micrometre, symbol μ or μm.^{[6][7][2][11]}
2. A unit of low pressure, equal to that of a column of mercury one micron high.^[6]

Word family

• chylomicron
• millimicron
• submicron
• micronize

Related words

• micro-
• micrometre

References

1. ^ a b c Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
4. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
5. ^ Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
6. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins
8. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
9. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
10. ^ a b Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press
11. ^ The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin