Definition of Duality

Noun: duality d(y)oo'a-li-tee

Being twofold; a classification into two opposed parts or subclasses
- dichotomy
(physics) the property of matter and electromagnetic radiation that is characterized by the fact that some properties can be explained best by wave theory and others by particle theory
- wave-particle duality
(geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry