Definition:Dual


 * Relation Theory:
 * Dual Relation


 * Order Theory:
 * Dual Ordering
 * Dual Statement
 * Dual Isomorphism
 * Dual Order Embedding
 * Dual Pairs
 * Self-Dual


 * Linear Algebra:
 * Algebraic Dual
 * Ordered Dual Basis
 * Definition:Dual Vector Space


 * Category Theory:
 * Dual Category
 * Dual Statement


 * Geometry:
 * Dual Polyhedron

The concept of duality also appears in the context of De Morgan's Laws.

Also see

 * Definition:Self-Dual
 * Duality Principle