selenium

noun

se·​le·​ni·​um sə-ˈlē-nē-əm 

: a photosensitive element that occurs in both crystalline and amorphous forms, is obtained chiefly as a by-product in copper refining, and is used especially in glass, semiconductor devices, and alloys see Chemical Elements Table

Examples of selenium in a Sentence

Recent Examples on the Web

Calcium is important for bone strength and nerve signaling, manganese helps support metabolism and antioxidant defenses, copper plays a role in iron metabolism and energy production and selenium is essential for thyroid function and immune health. —Daryl Austin, USA Today, 21 Mar. 2026

Fish also supplies key brain nutrients like vitamin B12, vitamin D, selenium, and magnesium. —Lindsey Desoto, Health, 11 Mar. 2026

Beyond omega-3s, salmon also delivers high-quality protein, vitamin D and selenium — nutrients that work together in a way that cardiologists say supplements alone cannot replicate. —Deirdre Bardolf, FOXNews.com, 9 Mar. 2026

The selenium in mushrooms also helps your body make antioxidants that prevent cell damage, Zumpano said, and the vitamin B6 helps your body make red blood cells and supports your central nervous system. —Maggie O'Neill, Verywell Health, 8 Mar. 2026

Word History

Etymology

New Latin, from Greek selēnē moon, from selas brightness

First Known Use

1818, in the meaning defined above

Phrases Containing selenium

• selenium cell

Rhymes for selenium

• asplenium
• delphinium
• perineum
• proscenium
• ruthenium
• vaccinium
• rhenium

Kids Definition

selenium

noun

se·​le·​ni·​um sə-ˈlē-nē-əm 

: an element that is sensitive to light and is used especially in glass, alloys, and electronic devices see element

Medical Definition

selenium

noun

se·​le·​ni·​um sə-ˈlē-nē-əm 

: a nonmetallic photosensitive element that occurs in both crystalline and amorphous forms, is an essential trace element found especially in grains and meat, and is used chiefly in glass, semiconductor devices, and alloys

—symbol Se see Chemical Elements Table, selenosis