selenium

se·le·ni·um   (sĭ-lē'nē-əm)    n.   Symbol Se 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. [Greek selēnē, moon (from selas, light, brightness) + -ium.]

Main Entry: se·le·ni·um
Pronunciation: s&-'lE-nE-&m
Function: noun
: a nonmetallic element that resembles sulfur and telluriumchemically, causes poisoning in range animals when ingested by eating some plants growing in soils in which it occurs in quantity, and occurs in allotropic forms of which a gray stable form varies inelectrical conductivity with the intensity of its illumination and is used in electronic devices —symbol Se; —see ELEMENT table

selenium se·le·ni·um (sĭ-lē'nē-əm)
n.
Symbol Se
A nonmetallic element, with red, black, and gray allotropic forms, resembling sulfur and obtained primarily as a byproduct of electrolytic copper refining. Atomic number 34; atomic weight 78.96; melting point (of gray selenium) 221°C; boiling point (gray) 684.9°C; specific gravity (gray) 4.79; (black) 4.28; valence 2, 4, or 6.