开元

Tang emperor Xuanzong's 唐玄宗[Tang2 Xuan2 zong1] reign name used during the Kaiyuan era (713-741), a peak of Tang prosperity

to open / to start / to turn on / to boil / to write out (a prescription, check, invoice etc) / to operate (a vehicle) / carat (gold) / abbr. for Kelvin, 開爾文|开尔文[Kai1 er3 wen2] / abbr. for 開本|开本[kai1 ben3], book format

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