Being twofold; a classification into two opposed parts or subclasses.

synonym: dichotomy.

Roget 89: duality, dualism; duplicity; biplicity^†, biformity^†; polarity.    two, deuce, couple, duet, brace, pair, cheeks, twins, Castor and Pollux, gemini, Siamese twins; fellows; yoke, conjugation; dispermy^†, doublets, dyad, span.    ... show more

Dutch: tweedeling, dichotomie
Polish: dualizm, dwoistość, dychotomia, dychotomiczność

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.

synonym: wave-particle duality.

Polish: dualizm falowo-korpuskularny

geometry The interchangeability of the roles of points and planes in the theorems of projective geometry.