rare earth vs lanthanide

rare earth and lanthanide both are nouns.

Word	Noun	Adjective	Verb	Adverb
rare earth	Yes	No	No	No
lanthanide	Yes	No	No	No

As nouns, rare earth and lanthanide are synonyms defined as:

rare earth and lanthanide: any element of the lanthanide series (atomic numbers 57 through 71)

Other synonyms of rare earth include lanthanoid, lanthanon, rare-earth element.

rare earth (noun)	lanthanide (noun)
any element of the lanthanide series (atomic numbers 57 through 71)	any element of the lanthanide series (atomic numbers 57 through 71)