refractive

Etymology

It is formed from English refract + -ive,^[1][2][3] or from Latin refract-, the past participial stem of refringō (“to break up, deflect”), with the same suffix.^[1] The Latin verb is formed from re- (“back”) and frangō (“to break”),^[4][3] from Proto-Indo-European *bhreg- (“to break”).^[3][4] Etymonline and Dictionary.com also name Late Latin refractīvus, which was used of pronouns in the sense "reflexive";^[3][5] the OED cites that word, from Priscian in the 5th or 6th century, only for comparison, together with French réfractif (“causing refraction”), recorded from 1706.^[1] According to the OED, the obsolete Scots sense "stubborn" and the medical sense "resistant to infection" were apparently influenced by refractory.^[1]

Earliest recorded meaning

Stubborn, obstinate or rebellious, a rare Scots sense: 1623, in the records of the Perth Kirk Session.^[1][2] The optical sense, able to refract light, follows in 1642,^[1][6] and is the first sense in Etymonline, which dates the word to the 1670s;^[3] the 1989 edition of the OED and Merriam-Webster's Collegiate gave 1673,^[7][8] and Dictionary.com gives 1665–75.^[5]

Semantic evolution

The "stubborn" sense did not last beyond the early 18th century.^[1][2] The optical sense took its place, and led to "due to or caused by refraction" (1717, in Berkeley's journals of his Italian travels) and "of or relating to refraction" (1727, in Thomson's poem to the memory of Newton).^[1] Johnson (1755) defined the word only as "having the power of refraction", quoting Newton's Opticks.^[9] The phrases refractive power (1709) and refractive index (1839) belong to the language of optics,^[7] and in ophthalmology the word came to describe the parts of the eye that bend light.^[1] In 1908 medicine and biology took it up for "resistant to infection or a parasite", a use that the OED compares with refractory.^[1]

Timeline

• 1623 – in Scots, stubborn, obstinate (obsolete by 1709).^[1]
• 1642 – that refracts light; having the power of refraction.^[1][6]
• 1709 – refractive power, the power of a transparent body to refract light.^[7]
• 1717 – due to or caused by refraction.^[1]
• 1727 – of or relating to the refraction of light.^[1]
• 1812 – that has undergone refraction.^[1]
• 1839 – refractive index.^[7]
• 1908 – in medicine and biology, resistant to infection or a parasite.^[1]

Meanings

Adjective

1. Able to refract light or other radiation; causing refraction: The refractive layers of the crystal split the beam into colours.^[10][6][1]
2. Relating to or caused by refraction; in ophthalmology, relating to the parts of the eye that bend light: The refractive power of the eye changes with age.^[6][1][11]
3. refractive index: a measure of how much a substance bends light that passes into it.^[2][7]
4. (medicine and biology) Resistant to an infection or a parasite.^[1]
5. (obsolete, 1623–1709) Stubborn, obstinate.^[1][2]

Word family

• refractively
• refractiveness
• refractivity
• nonrefractive
• unrefractive
• refractive index

Related words

• refract
• refraction
• refractory
• fracture
• fragment

References

1. ^ a b c d e f g h i j k l m n o p q r s t u v Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
2. ^ 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
3. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
4. ^ a b The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
5. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
6. ^ a b c d Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
7. ^ a b c d e Simpson, J. A.; Weiner, E. S. C., eds. (1989), The Oxford English Dictionary, 2nd ed., Oxford: Clarendon Press
8. ^ Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
9. ^ Johnson, Samuel (1755), A Dictionary of the English Language, London; 4th ed. 1773; Johnson's Dictionary Online, ed. Beth Rapp Young et al.
10. ^ Collins English Dictionary (2023), Glasgow: HarperCollins
11. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press