1. A soft, silvery-white metallic chemical element of the lanthanide series, used in alloys, catalysts, and optical materials.
Usage: chemistry; symbol: La; atomic number: 57

Examples

• Lanthanum is one of the rare earth elements found in the lanthanide group.
• The catalyst contains lanthanum compounds that improve the efficiency of the chemical reaction.
• Lanthanum alloys are used in lighter flints and battery electrodes.
• Scientists discovered lanthanum in 1839 in a mineral called cerite.
• Lanthanum oxide is added to optical glass to increase its refractive index.