English noun: atomic number 90 | |||
1. | atomic number 90 (substance) a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands | ||
Synonyms | Th, thorium | ||
Broader (hypernym) | metal, metallic element | ||
Narrower (hyponym) | radiothorium, thorium-228 | ||
Substance meronym | monazite, thorite | ||