diffusion

Etymology

It is inherited from Middle English diffusioun,^[2][3] borrowed from Latin diffūsiō (“a pouring forth, spreading”),^{[4][5][6][7][8]} and according to Etymonline and the MED partly also borrowed from Old French diffusion;^[9][2] the OED notes that the French word is recorded only from the later 15th century and is rare before the late 16th.^[4] In Latin the noun meant expansiveness of mind, and later also extent, the pouring out of liquids (about 400) and copiousness of writing (6th century).^[4] It is formed on diffūsus, the past participle of diffundō (“to pour out, scatter”),^[9][4][5] from dis- (“apart, in every direction”) and fundō (“to pour”).^[9][6]

Earliest recorded meaning

Copiousness of speech, prolixity: Chaucer's Troilus and Criseyde, written about 1385, in the phrase diffusioun of speche.^[4][2]

Semantic evolution

The literal sense "a pouring out, effusion" is recorded from about 1484 and died out by 1832.^[4][7] The sense now usual, the spreading of something over a wide area, dates from 1585 in the OED^[4] and the 1590s in Etymonline,^[9] and Johnson (1755) gave "dispersion; the state of being scattered every way" first and "copiousness; exuberance of style" second.^[10] For the spreading of knowledge or ideas the OED has a record from 1600,^[4] where Etymonline gives 1750.^[9] The scientific sense, the spontaneous mixing of two substances, especially gases or liquids, without chemical combination, dates from 1725.^[4] The 19th century added uses in psychology (1859), anthropology, for the spread of a culture's elements from one people to another (1871, in Tylor's Primitive Culture), linguistics (1874) and economics, for the spread of new products and ideas (1890).^[4] The old sense "prolixity" is now rare.^[4]

Timeline

• c. 1385 – copiousness of speech, in Chaucer.^[4][2]
• c. 1484 – a pouring out (obsolete by 1832).^[4]
• 1585 – spreading through a space or over a surface.^[4]
• 1600 – the spreading of knowledge or ideas.^[4]
• 1725 – the spontaneous mixing of substances.^[4]
• 1755 – Johnson: "dispersion; the state of being scattered every way".^[10]
• 1871 – in anthropology, the spread of cultural elements.^[4]
• 1890 – the spread of innovations in a society or economy.^[4]

Meanings

Noun

1. The spreading of something over a wide area or among many people; dispersion: the diffusion of new farming methods across the region.^[11][12][4]
2. (physics, chemistry) The gradual mixing of molecules or ions through their random thermal motion, from a region of higher concentration to one of lower.^[11][12][4]
3. (physics) The scattering of light or other radiation in many directions.^[12]
4. (anthropology) The spread of elements of a culture from one people or region to another.^[4]
5. (rare) Wordiness; prolixity.^[11][12][4]
6. (obsolete, 1484–1832) A pouring out; effusion.^[4][7]

Word family

• diffusional
• diffusionism
• diffusionist
• immunodiffusion
• interdiffusion
• rediffusion
• self-diffusion
• thermodiffusion

Related words

• diffuse
• effusion
• fusion
• confuse
• transfusion
• profuse
• refund

References

1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
2. ^ a b c d Kurath, Hans; Kuhn, Sherman M.; Lewis, Robert E., eds. (1952–2001), Middle English Dictionary, Ann Arbor: University of Michigan Press; online edition ed. Frances McSparran et al. (2000–2018)
3. ^ Benson, Larry D., Glossarial Concordance to Middle English (Chaucer, Gower), Johns Hopkins University, github.com/jhu-digital-manuscripts/gcme
4. ^ 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
5. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
7. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
8. ^ Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
9. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
10. ^ 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.
11. ^ a b c Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
12. ^ a b c d Collins English Dictionary (2023), Glasgow: HarperCollins