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

  • n. A nonmetallic element, red in powder form, black in vitreous form, and metallic gray in crystalline form, resembling sulfur and obtained primarily as a byproduct of electrolytic copper refining. It is widely used in rectifiers, as a semiconductor, and in xerography. Its photovoltaic and photoconductive actions make it useful in photocells, photographic exposure meters, and solar cells. Atomic number 34; atomic weight 78.96; melting point (of gray selenium) 217°C; boiling point (gray) 684.9°C; specific gravity (gray) 4.79; (vitreous) 4.28; valence 2, 4, or 6. See Table at element.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A nonmetallic chemical element (symbol Se) with an atomic number of 34.

from the GNU version of the Collaborative International Dictionary of English

  • n. A nonmetallic element of the sulphur group of atomic number 34, analogous to sulphur in its compounds. It is found in small quantities with sulphur and some sulphur ores, and obtained in the free state as a dark reddish powder or crystalline mass, or as a dark metallic-looking substance. It exhibits under the action of light a remarkable variation in electric conductivity, and is used in certain electric apparatus. Symbol Se. Atomic weight 78.96.

from The Century Dictionary and Cyclopedia

  • n. Chemical symbol, Se; atomic weight, 79.5. A non-metallic element extracted from the pyrite of Fahlun in Sweden, and discovered in 1818 by Berzelius.

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

  • n. a toxic nonmetallic element related to sulfur and tellurium; occurs in several allotropic forms; a stable grey metallike allotrope conducts electricity better in the light than in the dark and is used in photocells; occurs in sulfide ores (as pyrite)


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

Greek selēnē, moon (from selas, light, brightness) + -ium.

from Wiktionary, Creative Commons Attribution/Share-Alike License

A New Latin word derived by Swedish chemist Berzelius in 1818, from Ancient Greek Σελήνη (selēnē, "moon").


  • As I pointed out (but which whizzed 40,000 feet over your head), selenium is also "necessary for life", but nonetheless a toxic pollutant at higher concentrations (and regulated by the EPA).


  • If he was just a little bit scientifically inclined, he'd also know that while selenium is an essential cofactor for enzymes necessary to life, it is nonetheless toxic pollutant at high concentrations, and subject to air pollution regulations.


  • I shall probably have to use the metal called selenium, which is very sensitive to light, and which makes a good or a poor electrical conductor according as more or less light falls on it.

    Tom Swift and His Photo Telephone or the Picture That Saved a Fortune

  • As of this writing the file is called selenium-java-2.


  • A substance called selenium, when treated to broccoli, showed that the amount of one of the cancer-fighting compounds in broccoli was six times higher than in regular broccoli.

    Daily News & Analysis

  • A decade ago, Westlands floated a bond to buy 100,000 acres of farm land where poor drainage had created a salt buildup called selenium, making the land unusable for growers. Home RSS feed

  • The company makes these panels from a combination of copper, indium, gallium and selenium, which is placed on a flexible foil.


  • Occupational Health Sciences Institute (EOHSI) which is jointly administered by UMDNJ-Robert Wood Johnson Medical School and Rutgers, The State University of New Jersey, have discovered that a form of a dietary trace element known as selenium can help reset a cell's "biological clock" when it is disrupted by a chemical breast cancer.


  • Washington, DC: Scientists have found that a form of the element selenium, which is found in tiny amounts in people's diets, can help reset a cell's biological clock after it has been thrown off by cancer-causing chemicals.


  • That compares, in the same amount of soil, with about 183,000 pounds of arsenic and 8,600 pounds of selenium, which is particularly toxic to fish and aquatic life. Top News


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  • Se

    December 2, 2007