Selenium

Part of speech: noun

Pronunciation: /sɪˈliːni.əm/

Definitions

1. A nonmetallic chemical element essential for certain biological processes, used in glass manufacturing, and found in some minerals and soils
2. A naturally occurring element that plays a role in nutrition for some organisms, commonly used in electronics, and important for photocells
3. An element that is vital for certain living organisms, utilized in the production of glass and pigments, and appears in minerals and as a byproduct of metal refining

Etymology: Berzelius named selenium in 1818 after a mix-up with its chemical neighbour. He had isolated an unfamiliar substance from the residues of sulphuric acid production, and it looked and behaved so much like tellurium, an element already known, that he initially took it for a variant of that metal. Tellurium takes its name from the Latin for earth, so Berzelius went looking for a companion name in the sky. He chose the Greek word for moon, "selḗnē," and the new element became the lunar partner of the earthly tellurium. The name passed into French as "sélénium" before reaching English. The pairing is a neat accident of naming: the two elements sit side by side in the periodic table and share chemical traits, and the moon-and-earth naming scheme was Berzelius's own invention to reflect that resemblance.