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invariant

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Etymology and origin of the English word invariant

Confidence
Established
Formation
Derivation
First attested
1851 J. J. Sylvester, in the London, Edinburgh, & Dublin Philosophical Magazine More words from the 19th century
Ultimate origin
Latin variō
Etymology tree
inherited borrowed derived
English variant
English invariant

Pronunciation

  • UK: /(ˌ)ɪnˈvɛːriənt/[1]
  • US: /ˌɪnˈvɛriənt/, /ᵻnˈvɛriənt/[1]

Etymology

It is formed from English in- (“not”) + variant.[1][2][3][4][5] Variant is from Old French variant and Latin variāns, the present participle of variō (“to change, vary”).[2][6]

Earliest recorded meaning

As a noun in mathematics, a function of the coefficients of a quantic that keeps its value, up to a factor, when the quantic is transformed linearly: 1851, in J. J. Sylvester.[1] Etymonline dates the noun to 1851 as well, but the adjective "remaining always the same" to 1795;[2] the OED's first record of the adjective, "unvarying", is from G. H. Lewes in 1874,[1] the date Merriam-Webster also gives.[7][3] Dictionary.com dates the word to 1850–55.[5]

Semantic evolution

The word began as a technical term of the new algebra of invariants in the 1850s.[1][2] The general adjective "unvarying" followed in 1874,[1][7] and in 1899 physical chemistry used it of a system with no degrees of freedom.[1] From 1908 the adjective meant unchanged by a given transformation or operation, usually with under, and the noun widened to any quantity or expression with that property.[1] In 1939 the noun was first used in general of an unchanging property or feature.[1]

Timeline

  • 1851 – noun, in mathematics, a function of the coefficients of a quantic unchanged by linear transformation.[1][2]
  • 1874 – adjective, unvarying, invariable.[1][7]
  • 1899 – adjective, in physical chemistry, having no degrees of freedom.[1]
  • 1908 – adjective, unchanged by a specified transformation; noun, any quantity unchanged in this way.[1]
  • 1939 – noun, in general, an unchanging property or feature.[1]

Meanings

Adjective

  1. Never varying; constant: The colour of the signal stays invariant whatever the weather.[8][3][1]
  2. (mathematics, physics) Unchanged by a specified transformation or operation: invariant under rotation.[8][3][1]
  3. (physical chemistry) Having no degrees of freedom.[1][3]

Noun

  1. (mathematics) A quantity, function or expression that stays the same under a specified transformation or operation.[8][3][1]
  2. A property or feature that does not change.[1][3]

Word family

  • invariance
  • invariantly

References

  1. ^ a b c d e f g h i j k l m n o p q r s t Oxford English Dictionary Online (accessed March 2026), Oxford: Oxford University Press
  2. ^ a b c d e Harper, Douglas. Online Etymology Dictionary, https://www.etymonline.com
  3. ^ a b c d e f g Merriam-Webster Unabridged Dictionary (2024), online ed., Springfield, Mass.: Merriam-Webster
  4. ^ Shorter Oxford English Dictionary on Historical Principles (2002), 5th ed., ed. William R. Trumble and Angus Stevenson, Oxford: Oxford University Press
  5. ^ a b Dictionary.com Unabridged (2016), based on the Random House Unabridged Dictionary, New York: Random House
  6. ^ The American Heritage Dictionary of the English Language (online 2024), 5th ed., Boston: Houghton Mifflin Harcourt
  7. ^ a b c Merriam-Webster's Collegiate Dictionary (2003), 11th ed., Springfield, Mass.: Merriam-Webster
  8. ^ a b c The American Heritage Dictionary of the English Language (1992), 3rd ed., Boston: Houghton Mifflin

Related etymologies

Cite this entry

“Invariant.” Etymologically, 8 Nov. 2026, etymologically.com/en/invariant. Accessed 9 Nov. 2026.

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