Definition of lanthanum in English:



  • The chemical element of atomic number 57, a silvery-white rare earth metal.

    • ‘Green light is also emitted from some lanthanide elements: lanthanum, cerium, and terbium.’
    • ‘Samarium is a rare earth element, one of the elements that occupy the space in Row 6 of the periodic table between lanthanum and hafnium.’
    • ‘Oxalate efflux could not be triggered by treatment with the trivalent cation lanthanum or by phosphorus deficiency, indicating that the efflux was specific to the Al treatment.’
    • ‘It belongs to the family known as the lanthanides, named after the first member of that series, lanthanum.’
    • ‘Its chemical properties are similar to those of lanthanum, the element above it in the periodic table.’


Mid 19th century: from Greek lanthanein escape notice (because it was long undetected in cerium oxide) + -um.