any of the rare-earth elements (lanthanide series)
sometimes called lan′tha·noid· or lan′tha·non·
See rare-earth element.
Origin of lanthanidelanthan(um) + –ide.
- According to IUPAC - "Although lanthanoid means 'like lanthanum' and so should not include lanthanum, lanthanum has become included by common usage. Similarly, actinoid. The ending 'ide' normally indicates a negative ion, and therefore lanthanoid and actinoid are preferred to lanthanide and actinide. However, lanthanide and actinide are still allowed owing to wide current use."