dual

Definitions

• Exhibiting duality; characterized by having two (usually equivalent) components.
• Acting as a counterpart.
• Double.
• (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.
• (linear algebra) Being the space of all linear functionals of (some other space).
• (category theory) Being the dual of some other category; containing the same objects but with source and target reversed for all morphisms.