Duality

Duality may refer to:

Mathematics

 * Duality (mathematics), a mathematical concept
 * Dual (category theory), a formalization of mathematical duality
 * Duality (optimization)
 * Duality (order theory), a concept regarding binary relations
 * Duality (projective geometry), general principle of projective geometry
 * Duality principle (Boolean algebra), the extension of order-theoretic duality to Boolean algebras
 * S-duality (homotopy theory)

Philosophy, logic, and psychology

 * Dualistic cosmology, a twofold division in several spiritual and religious worldviews
 * Dualism (philosophy of mind), where the body and mind are considered to be irreducibly distinct
 * De Morgan's laws, specifically the ability to generate the dual of any logical expression
 * Complementary duality of Carl Jung's functions and types in Socionics
 * Duality (CoPs), refers to the notion of a duality in a Community of Practice

Electrical and mechanical

 * Duality (electrical circuits), regarding isomorphism of electrical circuits
 * Duality (mechanical engineering), regarding isomorphism of some mechanical laws

Physics

 * AdS/CFT correspondence (anti de Sitter/conformal field theory correspondence), sometimes called the Maldacena duality
 * Dual resonance model
 * Duality (electricity and magnetism)
 * Englert–Greenberger duality relation
 * Holographic duality
 * Kramers–Wannier duality
 * Mirror symmetry (string theory)
 * Montonen–Olive duality
 * Mysterious duality
 * String duality, a class of symmetries
 * S-duality
 * T-duality
 * U-duality
 * Wave–particle duality
 * Wave–particle duality

Albums

 * Duality (Peter Leitch and John Hicks album), 1994
 * Duality (Lisa Gerrard and Pieter Bourke album), 1998
 * Duality (Set It Off album), 2014
 * Duality (Ra album), 2005
 * Duality (mixtape), 2012
 * Duality (Luna Li album), 2022
 * Duality (Lindsey Stirling album), 2024
 * Duality, a 2009 album by Darker Half
 * Duality, a 2020 album by Duke Dumont
 * Duality, a 2018 album by Big Scoob

Songs

 * "Duality", a 2014 single from pop rock/punk rock band Set It Off
 * "Duality" (song), a 2004 single by metal band Slipknot
 * "Duality", a 2007 single from alternative rock/punk band Bayside

Other

 * Duality (film), a 2001 Star Wars fan film by Dave Macomber and Mark Thomas
 * Duality, a large format audio mixing console by Solid State Logic
 * Dual (grammatical number), grammatical number that some languages use in addition to singular and plural