a nonmetallic element that exists in several allotropic forms. It occurs free in volcanic areas and in sulphide ores, esp pyrite. The common form is a grey crystalline solid that is photoconductive, photovoltaic, and semiconducting: used in photocells, solar cells, and in xerography. Symbol: Se; atomic no: 34; atomic wt: 78.96; valency: –2, 4, or 6; relative density: 4.79 (grey); melting pt: 221°C (grey); boiling pt: 685°C (grey)
WordReference Random House Unabridged Dictionary of American English © 2025
se•le•ni•um
(si lē′nē əm),USA pronunciation n. [Chem.]
- Chemistry, Nutritiona nonmetallic element chemically resembling sulfur and tellurium, occurring in several allotropic forms, as crystalline and amorphous, and having an electrical resistance that varies under the influence of light. Symbol: Se;
at. wt.: 78.96;
at. no.: 34;
sp. gr.: (gray) 4.80 at 25°C, (red) 4.50 at 25°C.
- Greek selé̄n(ē) moon + Neo-Latin -ium -ium; named in allusion to its similarity to tellurium
- Neo-Latin (1818)
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'selenium' also found in these entries (note: many are not synonyms or translations):
SE
- Saticon
- Se
- black selenium
- chalcogen
- photoconductivity
- photonegative
- ruby glass
- selenic
- selenide
- seleniferous
- selenious
- selenium cell
- selenium rectifier
- stagger
- xerography