duality

noun

1. (countable, uncountable)A classification into two subclasses or opposed parts.

   “moral duality”

   “philosophical duality”

   “The novel explored the duality of good and evil.”

   “He was fascinated by the duality of human nature.”

2. (countable, uncountable)The interchangeability of points and planes.
3. (countable, uncountable)The mathematical equivalence of two seemingly different theoretical descriptions of a physical system.

   “wave-particle duality”