thorium
noun
tho·ri·um
ˈthȯr-ē-əm 
: a radioactive metallic element that is obtained especially from monazite and is usually associated with rare earths see Chemical Elements Table
Examples of thorium in a Sentence
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The abundance of thorium and similar radioactive elements would have generated additional heat, driving temperature differences of several hundred degrees throughout the nearside mantle during the moon's early history.
—
Sharmila Kuthunur, Space.com, 14 May 2025
Indeed, data from NASA's Lunar Prospector mission revealed the lunar nearside contains up to 10 times more thorium than lunar farside.
—Sharmila Kuthunur, Space.com, 14 May 2025
Previous studies had already revealed the presence of thorium consistent with KREEP impact melt along the floor of the basin, suggesting that the mantle material may have broken through the crust during the impact.
—Nola Taylor Tillman, Space.com, 5 May 2025
The differing levels of thorium found on the crust of the moon may also mean differing levels of water stored in the mantle.
—Joshua Rapp Learn, Discover Magazine, 29 Apr. 2025
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Sharmila Kuthunur, Space.com, 14 May 2025
Indeed, data from NASA's Lunar Prospector mission revealed the lunar nearside contains up to 10 times more thorium than lunar farside.
—Sharmila Kuthunur, Space.com, 14 May 2025
Previous studies had already revealed the presence of thorium consistent with KREEP impact melt along the floor of the basin, suggesting that the mantle material may have broken through the crust during the impact.
—Nola Taylor Tillman, Space.com, 5 May 2025
The differing levels of thorium found on the crust of the moon may also mean differing levels of water stored in the mantle.
—Joshua Rapp Learn, Discover Magazine, 29 Apr. 2025
See All Example Sentences for thorium
Cite this Entry
“Thorium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/thorium. Accessed 10 Jun. 2025.
Copy CitationKids Definition
thorium
noun
tho·ri·um
ˈthōr-ē-əm
ˈthȯr-
: a radioactive metallic element see element
Medical Definition
thorium
noun
tho·ri·um
ˈthōr-ē-əm, ˈthȯr-
: a radioactive metallic element that occurs combined in minerals and is usually associated with rare earths
—symbol Th
see Chemical Elements Table
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