Definition of lanthanum
: a white soft malleable metallic element that occurs in rare-earth minerals — see element table
Recent Examples of lanthanum from the Web
The iPhone contains a chorus of eight rare earth elements: neodymium, praseodymium, dysprosium, terbium, gadolinium, europium, lanthanum, and yttrium.
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Britannica.com: Encyclopedia article about lanthanum
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