lumen

Etymology

It is borrowed from Latin lūmen (“light; an opening”),^[2][3][4][5] used in New Latin for a passage or cavity.^[6][7][8] The name of the unit of light is borrowed from French lumen,^[9][10] coined in French in 1894 by the physicist André-Eugène Blondel.^[11][10] The Latin noun, with the stem lūmin-,^[7][3] comes from a suffixed form of Proto-Indo-European *leuk- (“light, brightness”),^[11][4] and is related to luminous and luminary.^[9][12]

Earliest recorded meaning

An opening, passage or canal in an animal body: 1873, in T. H. Green's Introduction to Pathology and Morbid Anatomy.^[2] Merriam-Webster's Unabridged and Etymonline also date this sense to 1873,^[6][11] and Dictionary.com to 1870–75.^[7]

Semantic evolution

The anatomical sense, from the Latin meaning "opening", spread to botany in 1887, for the cavity of a plant cell, and to surgery in 1889, for the bore of a tube in an instrument.^[2] The physical unit takes up the Latin meaning "light".^[5][11] It is first recorded in English in 1894, in the Electrical World,^[2] though Etymonline dates it to 1897 and Barnhart to 1898.^[11][10] It was defined by the light of one candle, later of one candela, and is now part of the International System of Units.^[2][3][8]

Timeline

• 1873 – an opening, passage or canal in an animal body.^[2][11][6]
• 1887 – in botany, the cavity of a plant cell.^[2]
• 1889 – the bore of a tube in a surgical instrument.^[2]
• 1894 – a unit of luminous flux.^[2] Etymonline dates it to 1897, Barnhart to 1898.^[11][10]

Meanings

Noun

1. The cavity or channel inside a tubular organ, such as a blood vessel or the intestine: Fatty deposits had narrowed the lumen of the artery.^[6][8][3]
2. The space enclosed by the walls of a plant cell.^[6][8]
3. The bore of a tube, such as a hollow needle or a catheter.^[6][3][2]
4. The SI unit of luminous flux, equal to the light that a uniform point source of one candela emits into one steradian (symbol lm).^[8][3][6]

Word family

• lumenal
• lumen-hour

Related words

• luminal
• lux
• luminous
• luminary
• illuminate

Usage notes

The plural is usually lumina in the anatomical senses and lumens for the unit,^[3] though both plurals are used.^[8][6]

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
4. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
5. ^ a b Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
6. ^ a b c d e f g h Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
8. ^ a b c d e f Collins English Dictionary (2023), Glasgow: HarperCollins
9. ^ a b Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
10. ^ a b c d Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
11. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
12. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.