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1. (n.) selenium
a nonmetallic element occurring in several allotropic forms and having an electrical resistance that varies under the influence of light.
Etymology: (< NL (1818) < Gk selēn(ē) moon + NL -ium -ium2)
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| Definition of 'selenium' |
Princeton's WordNet |
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1. (noun) selenium, Se, atomic number 34
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)
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| Definition of 'selenium' |
Webster Dictionary |
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1. (noun) selenium
a nonmetallic element of the sulphur group, and 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 78.9
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| Definition of 'selenium' |
U.S. National Library of Medicine |
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1. selenium
An element with the atomic symbol Se, atomic number 34, and atomic weight 78.96. It is an essential micronutrient for mammals and other animals but is toxic in large amounts. Selenium protects intracellular structures against oxidative damage. It is an essential component of GLUTATHIONE PEROXIDASE.
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| Definition of 'selenium' |
The Standard Electrical Dictionary |
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1. selenium
A non-metallic element. It is interesting electrically on account of the changes its electric resistance undergoes when it is subjected to light.
In one set of experiments it was found that diffused light caused the resistance to fall in the ratio of 11 to 9. Full sunlight reduced it to one-half. Of the spectrum colors red was most powerful and the ultra red region still more strongly affected its resistance.
The effect produced by exposure to light is instantaneous, but on removal to the dark only slowly disappears.
A vessel of hot water was found to have no effect, showing that short ether waves are essential to the effect.
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