الاتحاد الدولي للكيمياء البحتة والتطبيقية
The 1985 International Union of Pure and Applied Chemistry "Red Book" (p. 45) recommends that "lanthanoid" is used rather than "lanthanide". The ending "-ide" normally indicates a negative ion. However, owing to wide current usage, "lanthanide" is still allowed and is roughly analogous to rare earth element.