- the series of rare-earth elements of atomic numbers 57 through 71 (lanthanum through lutetium).
Origin of lanthanide series
First recorded in 1940–45
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
- a class of 15 chemically related elements with atomic numbers from 57 (lanthanum) to 71 (lutetium)