selenium

3 definitions found

selenium - Collaborative International Dictionary of English v.0.48 :

  Selenium \Se*le"ni*um\, n. [NL., from Gr. selh`nh the moon. So
     called because of its chemical analogy to tellurium (from L.
     tellus the earth), being, as it were, a companion to it.]
     (Chem.)
     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.
     [1913 Webster]

selenium - WordNet (r) 2.1 (2005) :

  selenium
      n 1: 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) [syn: selenium, Se, atomic number 34
           ]

selenium - Elements (07Nov00) :

  selenium
  Symbol: Se
  Atomic number: 34
  Atomic weight: 78.96
  Metalloid element, belongs to group 16 of the periodic table. Multiple
  allotropic forms exist. Chemically resembles sulphur. Discovered in 1817
  by Jons J. Berzelius.