[thawr-ee-uh m, thohr-]

noun Chemistry.

a grayish-white, lustrous, somewhat ductile and malleable, radioactive metallic element present in monazite: used as a source of nuclear energy, as a coating on sun-lamp and vacuum-tube filament coatings, and in alloys. Symbol: Th; atomic weight: 232.038; atomic number: 90; specific gravity: 11.7.

Nearby words

  1. thorfinn karlsefni,
  2. thoria,
  3. thorianite,
  4. thoric,
  5. thorite,
  6. thorium dioxide,
  7. thorium series,
  8. thorn,
  9. thorn apple,
  10. thorn in one's flesh

Compare thoria.

Origin of thorium

< New Latin (1829); see Thor, -ium

Related formsthor·ic [thawr-ik, thor-] /ˈθɔr ɪk, ˈθɒr-/, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for thoric



a soft ductile silvery-white metallic element. It is radioactive and occurs in thorite and monazite: used in gas mantles, magnesium alloys, electronic equipment, and as a nuclear power source. Symbol: Th; atomic no: 90; atomic wt: 232.0381; half-life of most stable isotope, 232 Th: 1.41 × 10 10 years; valency: 4; relative density: 11.72; melting pt: 1755°C; boiling pt: 4788°C
Derived Formsthoric, adjective

Word Origin for thorium

C19: New Latin, from Thor + -ium

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for thoric



rare metallic element, 1832, Modern Latin, named 1828-9 by its discoverer, Swedish chemist Jöns Jakob Berzelius (1779-1848) in honor of the Scandinavian god Thor.

Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for thoric



n. Symbol Th

A radioactive metallic element that is used in magnesium alloys; its longest-lived isotope, Th 232, has a half-life of 1.41 X 1010 years. Atomic number 90.

The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for thoric




A silvery-white, radioactive metallic element of the actinide series. It is used for fuel in some nuclear reactors and for improving the high-temperature strength of magnesium alloys. The only naturally occurring isotope of thorium, Th 232, is also its most stable, having a half-life of 14.1 billion years. Atomic number 90; atomic weight 232.038; approximate melting point 1,750°C; approximate boiling point 4,500°C; approximate specific gravity 11.7; valence 4. See Periodic Table.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.