dual

adjective du.

1. not comparable Characterized by having two (usually equivalent) components. a dual-motor vehicle

   Similar: double, twin

2. not comparable Pertaining to two, pertaining to a pair of. dual engine failure

   Similar: double, duplicate, dual, duplex, duple, twissel, twofold, twosome

3. not comparable 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. not comparable Exhibiting duality.
5. not comparable 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.
6. not comparable 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.

   Similar: opposite

Similar: binary, double, dual, twin, twofold

noun duals · du.

1. Of an item that is one of a pair, the other item in the pair.
2. 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. The icosahedron is the dual of the dodecahedron.
3. The dual number.
4. 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.
5. A head-to-head match or meet between two teams, such as two high schools or colleges. Wrestling duals and meets take place at the Wisconsin Field House. There are no advance single event ticket sales.

verb duals · dualing · dualling · dualed · dualled

1. transitive To convert from single to dual; specifically, to convert a single-carriageway road to a dual carriageway. 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.