(n.) A metallic element found in certain rare minerals, as thorite, pyrochlore, monazite, etc., and isolated as an infusible gray metallic powder which burns in the air and forms thoria; -- formerly called also thorinum. Symbol Th. Atomic weight 232.0.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). thorium. Retrieved September 22, 2026, from http://smartdefine.org/thorium/definitions/2072208 |
| Chicago | Webster's. 2011. "thorium" http://smartdefine.org/thorium/definitions/2072208 (accessed September 22, 2026). |
| Harvard | Webster's 2011, thorium, Smart Define, viewed 22 September, 2026, <http://smartdefine.org/thorium/definitions/2072208>. |
| MLA | Webster's. "thorium" 28 May 2011. Web. 22 September 2026. <http://smartdefine.org/thorium/definitions/2072208> |