duality       
noun [ U ]  formal uk/dʒuːˈæl.ə.ti/ us/duːˈæl.ə.t̬i/
 双重性,二元性
the state of combining two different things
  His poems reveal the duality of his nature, the joy and hope, the fear and despair. 他的诗揭示了他的双重本性,既有欢乐且充满希望的一面,又有恐惧失望的一面。 
 Compare: dichotomy