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cerium

American

[seer-ee-uhm] / ˈsɪər i əm /

noun

a steel-gray, ductile metallic element of the rare-earth group found only in combination. Ce; 140.12; 58.

cerium British

/ ˈsɪərɪəm /

noun

a malleable ductile steel-grey element of the lanthanide series of metals, used in lighter flints and as a reducing agent in metallurgy. Symbol: Ce; atomic no: 58; atomic wt: 140.115; valency: 3 or 4; relative density: 6.770; melting pt: 798°C; boiling pt: 3443°C

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

cerium Scientific

/ sîr′ē-əm /

A shiny, gray metallic element of the lanthanide series. It is ductile and malleable and is used in electronic components, alloys, and lighter flints. It is also used in glass polishing, as a catalyst in self-cleaning ovens, and in various nuclear applications. Atomic number 58; atomic weight 140.12; melting point 795°C; boiling point 3,468°C; specific gravity 6.67 to 8.23; valence 3, 4.
See Periodic Table

Etymology

Origin of cerium

First recorded in 1795–1805; Cer(es) + -ium

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

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cerium

Valor has designed reusable ligands for 10 elements, including gold, copper, platinum, nickel and a number of otherwise difficult-to-isolate rare earths, including cerium, dysprosium and yttrium.

From The Wall Street Journal ● Mar. 11, 2026

The ore from MP’s External link Mountain Pass mine contains a lot of cerium, lanthanum, neodymium, praseodymium, and samarium.

From Barron's ● Nov. 13, 2025

"The objective of the liquid separation unit will be to purify cerium on one side, lanthanum on the other side," explains production manager Florian Gouneau as we walk up a flight of metal stairs.

From BBC ● Aug. 6, 2025

Inside this reactor, which contains a porous ceramic structure made of cerium oxide, a thermochemical cycle takes place for splitting water and CO2 captured previously from the air.

From Science Daily ● Oct. 27, 2023

The rare metals cerium, lauthanum, and didymium have been lately investigated by Drs. Hillebrand and Norton, in Bunsen's laboratory.

From The Galaxy, Volume 23, No. 2, February, 1877 by Various

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Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023