"rare-earth element." YourDictionary, n.d. Web. 10 December 2018. <https://www.yourdictionary.com/rare-earth-element>.
rare-earth element. (n.d.). Retrieved December 10th, 2018, from https://www.yourdictionary.com/rare-earth-element
Any of a group of 17 naturally occurring metallic elements that have similar properties, consisting of scandium, yttrium, and the 15 elements with atomic numbers 57 through 71 (the lanthanides). The rare-earth elements are widely used in electronics and other high-tech products.