An Etymological Dictionary of Astronomy and Astrophysics

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فرهنگ ریشه‌شناختی اخترشناسی-اخترفیزیک

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rare earth element
  بن‌پار ِ خاکی ِ کمیاب، خاک ِ کمیاب  
bonpâr-e xâki-ye kamyâb, xâk-e kamyâb
Fr.: terre rare  

Any of the group of metallic → chemical elements with → atomic numbers between 57 and 71 inclusive. The name is an inappropriate terminology, since they are neither rare nor earth; preferred name → lanthanide.

See also: → rare; → earth; → element.