• (British) enPR: dyo͞o'əl, djo͞o'əl; IPA: /ˈdjuː.əl/, /ˈdʒuː.əl/
  • (America) enPR: d(y)o͞o'əl; IPA: /ˈd(j)uː.əl/

dual (not comparable)

  1. Exhibiting duality; characterized by having two (usually equivalent) components.
  2. Acting as a counterpart.
  3. Double.
    a dual-headed computer
  4. (grammar) Pertaining to grammatical number (as in singular and plural), referring to two of something, such as a pair of shoes, in the context of the singular, plural and, in some languages, trial grammatical number.
    Modern Arabic displays a dual number, as did Homeric Greek.
  5. (linear algebra) Being the space of all linear functionals of (some other space).
    • 2012, Doug Fisher, Hans-J. Lenz, Learning from Data: Artificial Intelligence and Statistics V, Springer Science & Business Media ISBN 9781461224044, page 81
      Accordingly, a hyperplane in the sample space is dual to a subspace in the variable space.
  6. (category theory) Being the dual#Noun|dual of some other category; containing the same objects but with source and target reversed for all morphisms.
    • 1992, Colin McLarty, Elementary Categories, Elementary Toposes, Clarendon Press ISBN 9780191589492, page 77
      Every category is dual to its own dual, so if a statement holds in all categories so does its dual.
Synonyms Translations Translations Translations
  • French: duel
  • German: dual
  • Portuguese: dual
  • Russian: дво́йственный
  • Spanish: dual

dual (plural duals)

  1. Of an item that is one of a pair, the other item in the pair.
  2. (geometry) Of a regular polyhedron with V vertices and F faces, the regular polyhedron having F vertices and V faces.
    The octahedron is the dual of the cube.
  3. (grammar) dual number The grammatical number of a noun marking two of something (as in singular, dual, plural), sometimes referring to two of anything (a couple of, exactly two of), or a chirality-marked pair (as in left and right, as with gloves or shoes) or in some languages as a discourse marker, "between you and me". A few languages display trial number.
  4. (mathematics) Of a vector in an inner product space, the linear functional corresponding to taking the inner product with that vector. The set of all duals is a vector space called the dual space.
Translations Verb

dual (duals, present participle dualling; past and past participle dualled)

  1. (transitive) To convert from single to dual; specifically, to convert a single-carriageway road to a dual carriageway.
    • 1994, Great Britain. Parliament. House of Commons, Parliamentary Debates
      I have to declare an interest and I do so with some ambivalence because if the road is dualled it is likely to take half of my front garden.
    • 1998, Great Britain. Parliament. House of Commons, Parliamentary Debates
      Way back in 1971, the Government of the day first published plans for a high-capacity road network, which included the dualling of the A47 from King's Lynn to Great Yarmouth.
    • 2006, David Lowe, Intermodal Freight Transport, p. 163
      The power generation and propulsion systems are dualled to accommodate component failure and maintain propulsion at reduced speed should any part of one system be lost.

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