Duality principle

Duality principle or principle of duality may refer to:


 * Duality (projective geometry)
 * Duality (order theory)
 * Duality principle (Boolean algebra)
 * Duality principle for sets
 * Duality principle (optimization theory)
 * Lagrange duality
 * Duality principle in functional analysis, used in large sieve method of analytic number theory
 * Wave–particle duality