noun Chemistry.
a rare-earth, metallic element present in certain minerals and yielding colorless salts. Symbol: Tb; atomic number: 65; atomic weight: 158.924; specific gravity: 8.25.

1835–45; (Yt)terb(y), name of Swedish town where found + -ium. See ytterbium

terbic, adjective
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
Cite This Source Link To terbium
World English Dictionary
terbium (ˈtɜːbɪəm)
a soft malleable silvery-grey element of the lanthanide series of metals, occurring in gadolinite and monazite and used in lasers and for doping solid-state devices. Symbol: Tb; atomic no: 65; atomic wt: 158.92534; valency: 3 or 4; relative density: 8.230; melting pt: 1356°C; boiling pt: 3230°C
[C19: from New Latin, named after Ytterby, Sweden, village where it was discovered]

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
Cite This Source
American Heritage
Medical Dictionary

terbium ter·bi·um (tûr'bē-əm)
Symbol Tb
A soft metallic rare-earth element used in x-ray tubes. Atomic number 65; atomic weight 158.925; melting point 1,359°C; boiling point 3,221°C; specific gravity 8.23; valence 3, 4.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Cite This Source
American Heritage
Science Dictionary
terbium   (tûr'bē-əm)  Pronunciation Key 
Symbol Tb
A soft, silvery-gray metallic element of the lanthanide series. It is used in color television tubes, x-ray machines, and lasers. Atomic number 65; atomic weight 158.925; melting point 1,356°C; boiling point 3,123°C; specific gravity 8.229; valence 3, 4. See Periodic Table.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
Cite This Source
Encyclopedia Britannica


(Tb), chemical element, rare-earth metal of the lanthanoid series of the periodic table. One of the least abundant of the rare earths, terbium, when reduced to metallic form, is silvery white and is slowly oxidized by air at room temperatures and by cold water. The element was discovered in 1843 by Carl Gustaf Mosander in a heavy rare-earth fraction called yttria, but its existence was not confirmed for at least 30 years, and pure compounds were not prepared until 1905. Terbium occurs in many rare-earth minerals but is almost exclusively obtained as a by-product from monazite sands, which are a source of thorium. It is also found in the products of nuclear fission. Ion-exchange techniques are utilized for its commercial production. The metal is prepared in a highly pure form by thermoreduction of the anhydrous fluoride with calcium metal. At room temperature the atoms of the pure element adopt the hexagonal close-packed structure. The only isotope occurring in ores is terbium-159. About 20 radioactive artificial isotopes have been prepared, such as terbium-160 (73-day half-life). Sodium terbium borate as a laser material emits coherent light at 5,460 angstroms. In certain solid-state devices terbium is used to dope calcium fluoride, calcium tungstate, and strontium molybdate.

Learn more about terbium with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
Cite This Source
Example sentences
Meanwhile, terbium is used in lighting systems that are dramatically more energy-efficient than traditional incandescent lighting.
Sodium terbium borate is used in solid-state devices.
Copyright © 2014 Dictionary.com, LLC. All rights reserved.
  • Please Login or Sign Up to use the Recent Searches feature