- Rare earth is any of the seventeen metallic chemical elements found in atomic numbers 21, 39 and 57 through 71, typically found dispersed in deposits of chemicals with similar chemical properties.
An example of rare earth is cerium, a chemical oxidizing agent, that provides the yellow color in glass and acts as a catalyst for self-cleaning ovens.
- any of certain basic oxides much alike in physical and chemical properties; specif., any of the oxides of the rare-earth elements
- any of the rare-earth elements
- Any of various oxides of the rare-earth elements.
- A rare-earth element.
Origin of rare earthrare1 (because the minerals from which the rare-earth elements were first isolated are uncommon) + earth, metallic oxide.