sə̇ˈlēnēəm noun
( -s )
Etymology: New Latin, from selen- (I) + -ium; from the fact that it is related to an element the name of which ( tellurium ) derives from the Latin word for the planet earth ( tellus )
: a nonmetallic toxic element that is related to sulfur and tellurium and resembles them chemically, that occurs in allotropic forms including an amorphous red powder or black vitreous form, a red crystalline form, and a stable gray metallike form conducting electricity much more readily in the light than in the dark, that is found to a small extent in native sulfur and combined in native sulfides, in a few selenides (as clausthalite), and in various soils and plants, that is obtained usually as a by-product in the electrolytic refining of copper, and that is used chiefly in photoelectric cells, rectifiers, and other electronic devices, in decolorizing glass, and as a pigment especially for ruby glass and ceramic glazes and enamels — symbol Se ; compare element table