selenium
n.n. a chemical element that is a metal but is usually found in a solid form. It is used to make glass and to protect against certain types of damage to your body.
n. a nonmetallic chemical element with the symbol Se and atomic number 34. It is used in the production of glass, semiconductors, and as an essential trace mineral in biological systems.
Selenium is an important mineral for healthy hair and nails.
The glass manufacturer added selenium to the mixture to give the glass a deep red color.
While selenium is vital for the proper functioning of the immune system, excessive exposure to the element can lead to toxic effects on the nervous system and skin.
From French sélénium, the name coined by Swedish chemist Jöns Jacob Berzelius in 1818 from Ancient Greek σελήνη (selḗnē, “moon”) in reference to original confusion with the similar element tellurium.