noun
Chemistry term referring to a group of 17 metallic elements (scandium, yttrium, and the lanthanides). Often used in compounds like 希土類元素 (rare earth element) or 希土類磁石 (rare earth magnet).
希土類はハイテク製品に欠かせない。
Rare earths are essential for high-tech products.
この磁石に
Rare earths are used in this magnet.
Common loanword synonym for 'rare earth', often used in industrial and economic contexts. 希土類 is the native Sino-Japanese term more common in scientific literature.
Sino-Japanese compound: 希 (rare) + 土 (earth) + 類 (group/class). The spelling 稀土類 uses the older character 稀 (rare).