二元

duality / dual / bipolar / binary

two / 2 / (Beijing dialect) stupid

surname Yuan / the Yuan or Mongol dynasty (1279-1368)

currency unit (esp. Chinese yuan) / first / original / primary / fundamental / constituent / part / era (of a reign) / meta- (prefix) / (math.) argument / variable / (Tw) (geology) eon

dualism, belief that the universe is made of two different substance (e.g. mind and matter or good and evil)

ethyl alcohol C2H5OH