元古宙 Yuán gǔ zhòu 🔊 pre-Cambrian (geological eon 2500-645m) + Review this word Meanings Yuán gǔ zhòu name pre-Cambrian (geological eon 2500-645m) Its characters 元yuányuan (as written)HSK 1古gǔancientHSK 5宙zhòueternity