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From un- +‎ known, past participle of know. Compare Old English ungecnawen.


  • (UK) IPA(key): /ʌnˈnəʊn/
  • (US) enPR: ŭn-nōnʹ, IPA(key): /ʌnˈnoʊn/
  • (file)


unknown (comparative more unknown, superlative most unknown)

  1. (sometimes postpositive) Not known; unidentified; not well known.
    Synonyms: anonymous, unfamiliar, uncharted, undiscovered, unexplored, unidentified, unnamed, unrecognized, unrevealed, unascertained, obscure, unsung
    Antonyms: well-known, famous, known

Derived terms[edit]



unknown (plural unknowns)

  1. (algebra) A variable (usually x, y or z) whose value is to be found.
  2. Any thing, place, or situation about which nothing is known; an unknown fact or piece of information.
    • 1957, Ethel Erford Hewitt, Into the Unknown: An Historical Novel, page 351:
      Had God walked close beside her into the unknown?
    • 2003 [2002], Donald Rumsfeld, Hart Seely, editor, Pieces of Intelligence: The Existential Poetry of Donald H. Rumsfeld:
      As we know, There are known knowns. There are things we know we know. We also know There are known unknowns. That is to say We know there are some things We do not know.
    • 2020 April 9, Ian Boyd, “We practised for a pandemic, but didn’t brace”, in Nature, volume 580, number 7802, page 9:
      The other priority is getting people to respond well to interventions, especially changes to routine. This is one of the biggest unknowns in these scenarios, and yet compliance can be the most crucial factor in determining whether an intervention works.
  3. A person of no identity; a nonentity




  1. past participle of unknow