Etymologically
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rotor

This is the current revision of this entry, as edited by bogdan on 31 October 2026 at 15:19. This address is a permanent link to this version.
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Pronunciation

  • UK: /ˈɹəʊ.tə/[1]
  • US: /ˈɹoʊ.tɚ/, /ˈɹoʊ.tə/[1]

Etymology

It is an irregular clipping from English rotator,[2][3][4][5][6][7] which Barnhart compares with vector.[8] Rotator is from Latin rotātor (“one who makes something spin”), from rotō (“to turn round, revolve”).[3][2] The meteorological sense follows German Rotor, used by J. Küttner in 1938.[3]

Earliest recorded meaning

In mathematics, in the terminology of W. K. Clifford: a quantity with magnitude, direction and position, the simplest being a velocity of rotation about an axis (1873).[3][8][2]

Semantic evolution

Barnhart finds the later sense of a revolving part curiously derived from this mathematical one;[8] the mathematical sense is now rare.[5] The rotating part of an electric motor or dynamo is called a rotor from 1892,[3][9] and the rotating assembly of a turbine from 1903, the date Etymonline and Barnhart give for the mechanical sense.[3][2][8] It was also used of the rotor arm of an engine's distributor (1909) and the spinning container of a centrifuge (1913).[3] The lifting rotor of a helicopter or other rotary-wing aircraft is recorded from 1915 in the OED, but only from 1930 in Etymonline.[3][2] Later senses include the rotating cylinder of a ship driven by the Magnus effect (1924), the coding wheel of a cipher machine (1934), a rolling vortex of air in the lee of a mountain (1944) and, in cell biology, the turning part of the motor of a bacterial flagellum (1976).[3][10]

Timeline

  • 1873 – mathematics, a rotational quantity, in W. K. Clifford.[3][8][2]
  • 1892 – the rotating part of a motor or dynamo.[3][9]
  • 1903 – the rotating assembly of a turbine.[3][8][2]
  • 1909 – a rotor arm.[3]
  • 1915 – the lifting rotor of a rotary-wing aircraft.[3]
  • 1924 – a rotating cylinder used to propel a ship.[3]
  • 1934 – a disc in a cipher machine.[3]
  • 1944 – meteorology, a vortex of air with a horizontal axis.[3]
  • 1976 – cell biology, part of a bacterial flagellar motor.[3]

Meanings

Noun

  1. The rotating part of a machine, especially the armature of an electric motor or generator, or the rotating wheels of a turbine.[10][9][3]
  2. A system of rotating blades on a central hub that provides the lift for a helicopter or similar aircraft.[10][9][3]
  3. The revolving arm of the distributor in an internal-combustion engine.[10][3]
  4. A rolling wave of air in the lee of a mountain or hill, turning about a horizontal axis.[10][3]
  5. A tall rotating cylinder used to drive a ship.[9][3]
  6. (mathematics, now rare) A quantity representing a rotation rather than a straight displacement.[5][3]

Word family

  • rotorcraft

References

  1. ^ a b Wiktionary, the free dictionary, https://en.wiktionary.org
  2. ^ a b c d e f g Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  3. ^ a b c d e f g h i j k l m n o p q r s t u v w x Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  4. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  5. ^ a b c Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  6. ^ Stevenson, Angus, ed. (2010), Oxford Dictionary of English, 3rd ed., Oxford: Oxford University Press
  7. ^ Klein, Ernest. A Comprehensive Etymological Dictionary of the English Language. 2 vols. Amsterdam: Elsevier, 1966–1967.
  8. ^ a b c d e f Barnhart, Robert K. (1988), The Barnhart Dictionary of Etymology
  9. ^ a b c d e Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  10. ^ a b c d e Collins English Dictionary (2023), Glasgow: HarperCollins