Elements with atomic numbers 57 (Lanthanum) to 71 (Lutetium) inclusive plus scandium and yttrium.

A family of elements, consisting of scandium (atomic number 21), yttrium (atomic number 39), and the elements in the Lanthanides series, that chemically behave in similar ways because of the similarity in atomic structure, atomic radii and valances (3+ or 4+). Lanthanum, (atomic number 57), cerium, praseodymium, niodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, through lutetium (atomic number 71) are the elements in the lanthanide series.

series of elements usually taken to include elements with atomic numbers 58 to 71 (lanthanum) and sometimes yttrium and scandium.