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.

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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

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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

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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

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

The ECA’s report highlights that China supplies 96% of the EU’s magnesium, which is used to make hydrogen-generating electrolyzers, while Turkey provides 99% of boron used in solar panels.

From The Wall Street Journal • Feb. 2, 2026

For example, China supplies 97 percent of the EU's magnesium, used in hydrogen-generating electrolysers while Turkey provides 99 percent of the bloc's boron, used in solar panels.

From Barron's • Feb. 2, 2026

Electrolytes - minerals like sodium, potassium and magnesium - help regulate nerves, muscles and fluid balance in the body.

From BBC • Jan. 1, 2026

Then Mr. Hofacket ducked under his black veil and held up his magnesium flash powder.

From "The Evolution of Calpurnia Tate" by Jacqueline Kelly