thorium C2 Topic:Mathematics & Measurement US /ˈθɔːɹiəm/ See IPA manual Freq #57972 Meanings 1 noun a soft silvery-white tetravalent radioactive metallic element 2 noun A chemical element (symbol Th) with atomic number 90. A weakly radioactive, malleable, moderately hard silvery metal that tarnishes black when exposed to air. Thesaurus Synonyms 2 noun · a chemical element (symbol... thorinum Etymology From Thor + -ium. Topics Mathematics & Measurement External links Cambridge Dictionary Wiktionary Google Images # thorium **Type:** Word **Level:** C2 **Part of speech:** noun **IPA (US):** /ˈθɔːɹiəm/ **Frequency rank:** 57972 ## Meanings 1. a soft silvery-white tetravalent radioactive metallic element 2. A chemical element (symbol Th) with atomic number 90. A weakly radioactive, malleable, moderately hard silvery metal that tarnishes black when exposed to air. ## Etymology From Thor + -ium. ## Topics - Mathematics & Measurement markdown