magnesium

American  

[mag-nee-zee-uhm, -zhuhm, -shee-uhm] / mægˈni zi əm, -ʒəm, -ʃi əm /

noun

Chemistry.

1. a light, ductile, silver-white, metallic element that burns with a dazzling white light, used in lightweight alloys, flares, fireworks, in the manufacture of flashbulbs, optical mirrors, and precision instruments, and as a zinc substitute in batteries. Mg; 24.312; 12; 1.74 at 20°C.

---

magnesium British  

/ mæɡˈniːzɪəm /

noun

1. a light silvery-white metallic element of the alkaline earth series that burns with an intense white flame, occurring principally in magnesite, dolomite, and carnallite: used in light structural alloys, flashbulbs, flares, and fireworks. Symbol: Mg; atomic no: 12; atomic wt: 24.3050; valency: 2; relative density: 1.738; melting pt: 650°C; boiling pt: 1090°C

---

magnesium Scientific  

/ măg-nē′zē-əm /

1. A lightweight, moderately hard, silvery-white metallic element of the alkaline-earth group that burns with an intense white flame. It is an essential component of chlorophyll and is used in lightweight alloys, flash photography, and fireworks. Atomic number 12; atomic weight 24.305; melting point 649°C; boiling point 1,090°C; specific gravity 1.74 (at 20°C); valence 2.

2. See Periodic Table

---

Etymology

Origin of magnesium

From New Latin, dating back to 1800–10; see origin at magnesia, -ium

Compare meaning

How does magnesium compare to similar and commonly confused words? Explore the most common comparisons:

• magnesium vs. magnesium oxide

Explanation

Magnesium is a shiny metallic chemical element, and it's also a mineral that humans and other organisms need to be healthy. In nature, magnesium is only found combined with other elements, never on its own. When scientists isolate magnesium from these compounds, it looks silvery-white. Magnesium is an excellent conductor of electricity, and it burns brightly. It's used to make fireworks and flares, and it's often combined with aluminum and zinc to make lightweight metal alloys. Ionized magnesium is necessary for our bodies to function properly: It is involved in over 300 biochemical reactions in the human body. Many people take supplements containing magnesium compounds.

Example Sentences

“Lower levels of calcium and magnesium affect the strength of gluten,” said Pollack.

From The Wall Street Journal • May 9, 2026

The team placed a small dolomite crystal in a solution containing calcium and magnesium.

From Science Daily • Apr. 20, 2026

Bays said the meteor was spotted widely because it was "very bright", due to the chemical make up of the object, which included magnesium.

From BBC • Apr. 13, 2026

Because the sediment is rich in organic matter and nutrients like phosphorus, calcium, and magnesium, it can store these compounds and potentially release them back into the environment over time.

From Science Daily • Mar. 21, 2026

To solve the problem of repulsion, Crick had inserted a positively charged magnesium ion at the center of the helix—like a last-minute dab of molecular glue to hold the structure together.

From "The Gene" by Siddhartha Mukherjee