refraction

Etymology

It is borrowed from Late Latin refractiō (“a breaking up; resistance, opposition”),^[2][3][4][5] a noun of action formed on refractus, the past participle of refringō (“to break up; to deflect light rays”),^[2][3][5] which is from re- (“back”) and frangō (“to break”),^[2][3][6] from Proto-Indo-European *bhreg- (“to break”).^[3][6] The Latin noun meant resistance in the 4th century and logical conversion in the 6th, in Boethius, and was used of the deflection of a ray of light from 1267 in British sources.^[2] The Shorter Oxford also allows French réfraction as a source,^[7] and the OED compares Middle French réfraction, recorded in the optical sense in a manuscript of about 1369, along with Spanish refracción and Italian rifrazione.^[2] The verb refract is recorded from 1563, after the noun.^[2]

Earliest recorded meaning

A figure of rhetoric, the use of one word in opposing senses: 1555, in R. Sherry's Treatise of Figures of Grammar & Rhetorike.^[2] The optical sense follows in 1563, in W. Fulke's work on meteors, the first date that Merriam-Webster Unabridged gives.^[2][4] Etymonline dates the word to the 1570s,^[3] Dictionary.com to 1570–80,^[8] and the Oxford Dictionary of English to the mid 17th century.^[9]

Semantic evolution

The optical sense, already current in medieval Latin, is the one that lasted, while the rhetorical one remained rare and died out.^[2] From 1603 the word was applied in astronomy to the way the atmosphere deflects light from a celestial object and so raises its apparent altitude; from 1698 it also named the same effect on distant objects on land.^[2] Writers also kept the literal idea of breaking in English for a time: the action of breaking open or up is recorded from 1578 to 1661, and rebounding or recoiling from 1653 to 1661.^[2][7] From 1614, in Selden, it could be figurative, for the way a medium of expression or a personal view alters something pure or absolute.^[2] Johnson (1755) explained it through dioptrics, as a ray of light turned from its straight line by the density of the medium.^[10] Two technical uses were narrower: a reduction on a charge or bill (1728–82), which the OED compares with a French sense of a refund, and the amount of impurities in a sample of saltpetre, estimated since 1831 from the angle of refraction.^[2] In 1895 the Century Dictionary could call the word almost exclusively restricted to physics,^[3] but the early 20th century added the measurement of how the eye focuses.^[7]

Timeline

• 1555 – in rhetoric, the use of one word in opposing senses (obsolete).^[2]
• 1563 – the deflection of a ray of light in passing from one medium into another.^[2][4]
• 1578 – the action of breaking open or up (obsolete by 1661).^[2]
• 1603 – in astronomy, the deflection of a celestial object's light by the atmosphere.^[2]
• 1614 – figurative, the alteration of something by the medium it passes through.^[2]
• 1653 – rebounding, recoiling (obsolete by 1661).^[2]
• 1664 – the refractive power of a medium.^[2]
• 1698 – the atmosphere's effect on the look of objects on land.^[2]
• 1728 – a reduction on a charge or bill (obsolete by 1782).^[2]
• 1831 – in chemistry, the impurities in a sample of saltpetre.^[2]
• early 20th century – the measurement of how the eye focuses.^[7]

Meanings

Noun

1. The bending of a ray of light or other wave as it passes at an angle from one medium into another in which it travels at a different speed: The refraction of light in the pond made the oar look bent.^{[11][6][4][2]}
2. (astronomy) The apparent shift in the position of a celestial body, caused by the bending of its light in the Earth's atmosphere.^{[11][6][4][2]}
3. The power of a medium, or of the eye, to bend light.^[11][6][2]
4. The measurement of how an eye focuses light, as in testing for spectacles.^[11][7]
5. (figurative) The distortion of something by the medium through which it is expressed or the viewpoint from which it is seen.^[2]
6. (obsolete, 1578–1661) A breaking open or breaking up.^[2][7][4]
7. (obsolete, 1653–1661) A rebound or recoil.^[2][4]

Word family

• refractional
• nonrefraction
• angle of refraction
• index of refraction
• astronomical refraction
• double refraction

Related words

• refractive
• refractory
• refract
• fraction
• fragment
• diffraction
• reflection

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 x y z 27 28 29 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 d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
5. ^ a b Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
6. ^ a b c d e The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
7. ^ a b c d e f 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. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
10. ^ 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 d Collins English Dictionary (2023), Glasgow: HarperCollins