du.

Adjective

dual (not comparable)

1. Characterized by having two (usually equivalent) components.
   • a dual-motor vehicle

   Synonyms:

   double, twin

2. Pertaining to two, pertaining to a pair of.
   • dual engine failure

   Synonyms:

   double, duplicate, duplex, duple, twissel, twofold, twosome

3. Pertaining to a grammatical number in certain languages that refers to two of something, such as a pair of shoes.
   • Modern Arabic displays a dual number, as did Homeric Greek.
4. Exhibiting duality.
5. Being the space of all linear functionals of (some other space).
   • Accordingly, a hyperplane in the sample space is dual to a subspace in the variable space.2012, Doug Fisher, Hans-J. Lenz, Learning from Data: Artificial Intelligence and Statistics V, Springer Science & Business Media, →ISBN, page 81
6. Being the dual of some other category; containing the same objects but with source and target reversed for all morphisms.
   • Every category is dual to its own dual, so if a statement holds in all categories so does its dual.1992, Colin McLarty, Elementary Categories, Elementary Toposes, Clarendon Press, →ISBN, page 77

   Synonyms:

   opposite

See all 12 meanings of dual