[doo-al-i-tee, dyoo-]


a dual state or quality.
Mathematics. a symmetry within a mathematical system such that a theorem remains valid if certain objects, relations, or operations are interchanged, as the interchange of points and lines in a plane in projective geometry.

Origin of duality

1350–1400; Middle English dualitie < Late Latin duālitās. See dual, -ity
Related formsnon·du·al·i·ty, noun
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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noun plural -ties

the state or quality of being two or in two parts; dichotomy
physics the principle that a wave-particle duality exists in microphysics in which wave theory and corpuscular theory are complementary. The propagation of electromagnetic radiation is analysed using wave theory but its interaction with matter is described in terms of photons. The condition of particles such as electrons, neutrons, and atoms is described in terms of de Broglie waves
geometry the interchangeability of the roles of the point and the plane in statements and theorems in projective geometry
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for duality

late 14c., from Old French dualité (14c.), from Late Latin dualitas, from Latin dualis (see dual).

Online Etymology Dictionary, © 2010 Douglas Harper