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[loo-tee-shee-uh m] /luˈti ʃi əm/
noun, Chemistry
a trivalent rare-earth element. Symbol: Lu; atomic weight: 174.97; atomic number: 71.
Also, lutecium.
1905-10; < Latin Lūtēt(ia) Paris + -ium Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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British Dictionary definitions for lutetium


a silvery-white metallic element of the lanthanide series, occurring in monazite and used as a catalyst in cracking, alkylation, and polymerization. Symbol: Lu; atomic no: 71; atomic wt: 174.967; valency: 3; relative density: 9.841; melting pt: 1663°C; boiling pt: 3402°C
Word Origin
C19: New Latin, from Latin Lūtētia ancient name of Paris, home of G. Urbain (1872–1938), French chemist, who discovered it
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
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lutetium in Medicine

lutetium lu·te·ti·um or lu·te·ci·um (lōō-tē'shē-əm)
Symbol Lu
A rare-earth element, used in nuclear research. Atomic number 71; atomic weight 174.97; melting point 1,663°C; boiling point 3,393°C; specific gravity 9.841 (at 25°C); valence 3.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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lutetium in Science
Symbol Lu
A silvery-white metallic element of the lanthanide series that is used in nuclear technology. Its radioactive isotope is used in determining the age of meteorites. Atomic number 71; atomic weight 174.97; melting point 1,663°C; boiling point 3,395°C; specific gravity 9.840 (at 25°C); valence 3. See Periodic Table.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Article for lutetium

(Lu), chemical element, rare-earth metal of the lanthanoid series of the periodic table; the hardest and densest rare-earth element, last member of the lanthanoid series. Lutetium was discovered (1907-08) by Carl Auer von Welsbach and Georges Urbain, working independently. Urbain derived the name for the element from Lutetia, which was the ancient Roman name for Paris. The name Urbain gave it to honour Paris, his native city, became widely accepted, except in Germany, where it was commonly called cassiopeium until the 1950s. One of the rarest of the rare earths, lutetium occurs in rare-earth minerals such as xenotime and euxenite. Though it composes only about 0.003 percent of the commercially important mineral monazite, it has proved feasible to extract it as a by-product. Separation and purification are accomplished by ion-exchange techniques. Lutetium is also found in the products of nuclear fission. The metal has been prepared by thermoreduction of the anhydrous halides by alkali or alkaline-earth metals. It has the highest melting point of the rare-earth elements. Natural lutetium consists of two isotopes: stable lutetium-175 (97.41 percent) and radioactive lutetium-176 (2.59 percent, 3 1010-year half-life). The radioactive isotope is used to determine the age of meteorites relative to that of the Earth. Few other uses have been found for lutetium.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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