diffuse

Etymology

It is borrowed from Latin diffūsus (“spread out, extensive”), the past participle of diffundō (“to pour out, spread, scatter”),^[2][3][4][5] which is formed from dis- (“apart, in every direction”) and fundō (“to pour”),^[3][4][6] from Proto-Indo-European *gheu- (“to pour”).^[6] The adjective may also have come through Anglo-Norman diffus or Middle French diffus;^[6][7][8][9] the OED compares the French adjective, recorded in Old French from 1314, but takes the English one from Latin.^[2] The Anglo-Norman adjective is recorded from about 1270, meaning spread out or rambling.^[10] The verb was formed on the Latin past participial stem diffūs-, partly also by conversion of the adjective,^[2][8][11] and Merriam-Webster allows Middle French diffuser as a source too;^[12] the OED dates the French verb to the beginning of the 15th century.^[2] Klein and Skeat refer the Latin verb to fuse, to melt.^[5][13]

Earliest recorded meaning

The verb, to spread something abstract widely: before 1425, in the Northern Pauline Epistles.^[2] The adjective, in the sense "confused, obscure, hard to understand", follows in 1430, in the proceedings of the Privy Council;^[2] Barnhart dates it to 1413,^[14][4] and Etymonline to the early 15th century.^[3] Etymonline dates the verb only to the 1520s.^[3]

Semantic evolution

The first sense of the adjective, confused or obscure, died out by the early 17th century according to the Shorter Oxford,^[8] though the OED has it until 1817;^[2] Shakespeare used the verb once, in King Lear (1608), for "to make confused".^[2] The concrete sense, spread over a wide area or scattered, is recorded from about 1475,^[2][4][3] and the medical use, of a disease not confined to one part of the body, from 1585.^[2] Used of style, the adjective came to mean wordy or long-winded (1612 in the OED, earlier in Etymonline and the Shorter Oxford),^[2][3][8] and Johnson (1755) gave the two senses "scattered; widely spread" and "copious; not concise".^[15] Hoad notes that in the 18th century it became the opposite of confined and condensed.^[7] Later uses were technical: in botany of a loose, open panicle (1751), of light spread evenly and softened (1794), and in phonetics (1952).^[2] The verb meant to spread knowledge or ideas from before 1425, to send out light or sound in all directions from before 1475; from 1587 it also meant to scatter one's attention so as to weaken it;^[2] in physics and chemistry it was used for substances intermingling by diffusion from 1801, and intransitively from 1833.^[2]

Timeline

• before 1425 – verb, to spread something abstract among many people.^[2]
• 1430 – adjective, confused, obscure, hard to understand (obsolete).^[2]
• c. 1475 – adjective, spread over a wide area; scattered.^[2][4]
• 1541 – verb, to pour down or shower over something.^[2]
• 1585 – adjective, in medicine, not confined to one part of the body.^[2]
• 1608 – verb, to make confused, in Shakespeare's King Lear.^[2]
• 1612 – adjective, of style, wordy or verbose.^[2]
• 1655 – verb, intransitive, to spread widely.^[2] Etymonline dates this use to the 1650s.^[3]
• 1794 – adjective, of light, spread evenly and softened.^[2]
• 1801 – verb, in physics and chemistry, to intermingle by diffusion.^[2]

Meanings

Adjective

1. Spread out over a wide area; not concentrated: a diffuse network of small villages.^[16][12][2]
2. Using more words than needed; wordy or verbose: The report was too diffuse to hold the board's attention.^[16][12][2]
3. (medicine) Not localized; affecting a wide area of the body.^[12][2]
4. Of light, spread evenly so that it is soft and not harsh.^[16][2]
5. (botany) Spreading loosely or openly.^[16][12][2]
6. (obsolete, 1430–1817) Confused, obscure or hard to understand.^[2][12][8]

Verb

1. To spread widely, or make widely known; to disseminate: The new methods diffused slowly through the profession.^[16][12][2]
2. To send out or scatter in all directions, as light or heat.^[16][2]
3. (physics, chemistry) To intermingle, or cause to intermingle, by diffusion.^[16][2]
4. To spread thin, so as to weaken: He diffused his energy over too many projects.^[2][16]

Word family

• diffusely
• diffuseness
• diffusible
• diffusate
• interdiffuse
• nondiffuse
• overdiffuse
• rediffuse

Related words

• diffusion
• fuse
• fusion
• effuse
• profuse
• confuse
• infuse
• transfuse
• suffuse
• refund

Usage notes

The adjective ends in /s/ and the verb in /z/.^[2][16]

References

1. ^ a b 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 x y z 27 28 29 30 31 32 33 34 35 Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
3. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b c d e Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
5. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b c The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
7. ^ a b Hoad, T. F., ed. (1986), The Concise Oxford Dictionary of English Etymology, Oxford: Clarendon Press
8. ^ a b c d e Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
9. ^ Weekley, Ernest (1921), An Etymological Dictionary of Modern English, London: John Murray
10. ^ Anglo-Norman Dictionary (AND2), Aberystwyth University, anglo-norman.net (2nd ed., 2005–)
11. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
12. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
13. ^ Skeat, Walter W. (1911), A Concise Etymological Dictionary of the English Language, new ed., Oxford: Clarendon Press
14. ^ Barnhart, Robert K., ed. (1995), The Barnhart Concise Dictionary of Etymology, New York: HarperCollins
15. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
16. ^ a b c d e f g h i Collins English Dictionary (2023), Glasgow: HarperCollins