Definitions

from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. A brilliant, silvery, metallic element separated from ores of zirconium and used in nuclear reactor control rods, as a getter for oxygen and nitrogen, and in the manufacture of tungsten filaments. Atomic number 72; atomic weight 178.49; melting point 2,220°C; boiling point 5,400°C; specific gravity 13.3; valence 4. See Table at element.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A metallic chemical element (symbol Hf) with an atomic number of 72.

from the GNU version of the Collaborative International Dictionary of English

  • n. A metallic element of atomic number 72 present together with zirconium to the extent of 1% to 5% in zirconium minerals. It is a poisonous, ductile metal with a brilliant silver luster, has an atomic weight of 178.49, and has a high melting point (2227° C). It is used in nuclear reactors, and incandescent lamps as a scavenger of oxygen and nitrogen. See also norium.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons

Etymologies

After Hafnia, Medieval Latin name for Copenhagen, Denmark.
(American Heritage® Dictionary of the English Language, Fourth Edition)
From Latin Hafnia ("Copenhagen"). (Wiktionary)

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