diffraction

Etymology

It is borrowed from New Latin diffractiō (“a breaking in pieces”),^[2][3][4][5] from diffractus, the past participle of diffringō (“to break in pieces, shatter”),^[2][6][3] from dis- (“apart”) and frangō (“to break”),^[6][5][7] from Proto-Indo-European *bʰreg- (“to break”).^[6][5] The OED records the Latin noun from the 12th century in a British source, and in optics from Grimaldi's “Physico-mathesis de lumine” of 1665.^[2] Etymonline, Hoad and the Shorter Oxford allow a borrowing from French diffraction as well,^[6][7][8] which the OED records from 1666 in the optical sense.^[2] It is related to fraction and fragment.^[2][9]

Earliest recorded meaning

The action of breaking apart, a breakage: 1654, in Charleton's Physiologia Epicuro-Gassendo-Charltoniana, a sense now obsolete.^[2]

Semantic evolution

The general sense of breaking apart lasted until the 19th century,^[2] but the word survived as a term of optics for the spreading of light that passes a narrow slit or the edge of an opaque body, often with bands of colour, first recorded in English in the Philosophical Transactions of 1672.^[2][6] Merriam-Webster dates this sense to 1671, and Etymonline to the 1670s.^[3][6] From 1823 it was extended to other kinds of waves, and later to particles considered as waves.^[2] The verb diffract, recorded from 1803, is perhaps a back-formation from the noun.^[6]

Timeline

• 1654 – the action of breaking apart (obsolete by 1869).^[2]
• 1672 – in optics, the spreading of a beam of light past an edge or through a slit.^[2] Merriam-Webster dates it to 1671.^[3]
• 1823 – in physics, the same spreading in waves of any kind.^[2]

Meanings

Noun

1. In physics, the bending and spreading of waves, such as light or sound, as they pass the edge of an obstacle or go through a narrow opening.^[10][3][2]
2. The pattern of light and dark or coloured bands produced in this way.^[10][3]

Word family

• diffraction grating
• X-ray diffraction

Related words

• diffract
• fraction
• fracture
• fragment
• refraction
• reflection
• diffusion

References

1. ^ Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d e f g h i j k l m Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
4. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
5. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
6. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
7. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
9. ^ Partridge, Eric (1966), Origins: A Short Etymological Dictionary of Modern English, 4th ed., London: Routledge & Kegan Paul
10. ^ a b Collins English Dictionary (2023), Glasgow: HarperCollins