Definition of thorium in English:



mass noun
  • The chemical element of atomic number 90, a white radioactive metal of the actinide series.

    • ‘The concentrations of iron and thorium, for instance, have proved useful in distinguishing rock types from one another and in monitoring geochemical processes.’
    • ‘Deep within Earth, some diamonds come into contact with radioactive materials, such as thorium or uranium, that can impart a unique signature known as a radiation halo.’
    • ‘All natural rocks contain small amounts of uranium and thorium, which are radioactive and remain so for billions of years.’
    • ‘The analysis shows that manganese, titanium, hafnium, thorium, phosphorus, and the rare-earth elements play a significant role in discriminating between zircons of various origins.’
    • ‘In addition to primeval heat, Earth's core also gets heat from radioactive decay of uranium, thorium, and potassium.’


Mid 19th century: named after the god Thor.