名詞 duality:

1. being twofold; a classification into two opposed parts or subclasses
   同義詞：dichotomy
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
   同義詞：wave-particle duality
3. (geometry) the interchangeability of the roles of points and planes in the theorems of projective geometry

du.al.i.ty

n.（名詞）
The quality or character of being twofold; dichotomy.
兩重性：具有兩方面的性質或特點；一分為二