duality

noun

1. being twofold; a classification into two opposed parts or subclasses

Similar word(s): dichotomy

Definition categories: group, categorization, classification

2. (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

Definition categories: attribute, property

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

Definition categories: attribute, exchangeability, fungibility, interchangeability, interchangeableness