duality

Noun

• (geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry

• (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

• being twofold; a classification into two opposed parts or subclasses
  • the dichotomy between eastern and western culture
    

Related words

• Synonyms: 
  wave-particle duality , dichotomy