n.
Pronunciation: ' lan(t)-th ə - ˌ n ī d
Variant: also lan · tha · noid \ - ˌ no ̇ id \
Function: noun
Etymology: International Scientific Vocabulary
Date: 1926
: any of the series of elements with increasing atomic numbers that begins with lanthanum or cerium and ends with lutetium ― see PERIODIC TABLE table