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irradiation

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Etymology and origin of the English word irradiation

Confidence
Established
Formation
Borrowing
First attested
1589 Puttenham, The Arte of English Poesie
Borrowed from
French irradiation
Ultimate origin
Latin radius

Pronunciation

  • /ɪˌɹeɪdiˈeɪʃən/[1]

Etymology

It is borrowed from French irradiation,[2][3][4][5] from Late Latin irradiātiō,[4][6] a noun of action from irradiō (“to shine forth, illumine”),[3][2][4] formed from in- (“on, into”) and radiō (“to shine”),[3][7] from radius (“ray”).[7] Merriam-Webster calls the French source Middle French,[8] and the Shorter Oxford allows a borrowing from French or from Late Latin;[9] the OED, whose entry has not been fully revised, marks the Latin noun as unattested.[2]

Earliest recorded meaning

Figuratively, the enlightenment of the mind: 1589, in George Puttenham's Arte of English Poesie.[2] The literal sense, the giving out of rays of light, follows in 1599.[2][8] Etymonline dates the word to the 1580s, in reference to light both literally and figuratively,[3] and Dictionary.com to 1580–90.[6]

Semantic evolution

In the 17th century the word was used of rays and beams of light (1643) and of spiritual light (1631),[2][9] and older physiology used it for the supposed giving out of a fluid or influence from an active centre, including from the eye (1615–1706);[2][9] Bacon wrote of envy as an "irradiation of the eye".[9] Johnson (1755) defined it as the act of emitting beams of light.[5] Later senses followed the science of the day: the emission of heat rays (1794), the apparent enlargement of a brightly lit object seen against a dark background (1834),[2] and the scattering of light in a photographic emulsion (1924).[2][9] The sense now most common, exposure to radiation other than light, began with X-rays in 1901[3][9] and extended to the use of ionizing radiation in medicine and for preserving food.[7][10]

Timeline

  • 1589 – figuratively, enlightenment of the mind.[2]
  • 1599 – the giving out of rays of light.[2][8]
  • 1615 – in physiology, the supposed emission of a fluid or influence from a centre (obsolete by 1706).[2]
  • 1643 – a ray or beam of light.[2]
  • 1794 – the emission of heat rays.[2]
  • 1834 – in optics, the apparent enlargement of a bright object against a dark ground.[2]
  • 1901 – exposure to X-rays or other radiation.[3]
  • 1924 – in photography, the scattering of light in the emulsion.[2]

Meanings

Noun

  1. The act of exposing something to radiation, or the state of being exposed: Irradiation of the samples killed the bacteria.[7][10][9]
  2. The use of ionizing radiation, especially in medical treatment or to sterilize and preserve food.[7][10]
  3. The emission of radiant energy such as heat.[8][2]
  4. A spreading out from a common centre; in physiology, the spread of a nerve impulse beyond its usual path.[8][2]
  5. In optics, the apparent enlargement of a brightly lit object seen against a dark background.[10][2][9]
  6. In photography, the scattering of light in an emulsion, which blurs the image.[2][9]
  7. A ray or beam of light.[10][2][9]
  8. Figuratively, the enlightenment of the mind.[2][9]
  9. (archaic) The giving out of rays of light; shining.[8][2]

Word family

  • postirradiation
  • X-irradiation

References

  1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  3. ^ a b c d e f Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  4. ^ a b c Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
  5. ^ a b Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
  6. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
  7. ^ a b c d e The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  8. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  9. ^ a b c d e f g h i j k Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  10. ^ a b c d e Collins English Dictionary (2023), Glasgow: HarperCollins

Related etymologies

Cite this entry

“Irradiation.” Etymologically, 2 Nov. 2026, etymologically.com/en/irradiation. Accessed 2 Nov. 2026.

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