lanthanon vs rare-earth element

lanthanon and rare-earth element both are nouns.

Word	Noun	Adjective	Verb	Adverb
lanthanon	Yes	No	No	No
rare-earth element	Yes	No	No	No

As nouns, lanthanon and rare-earth element are synonyms defined as:

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

Other synonyms of lanthanon include lanthanide, lanthanoid, rare earth.

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