A soft silvery metallic element of the rare earth group; isotope 170 emits X-rays and is used in small portable X-ray machines; it occurs in monazite and apatite and xenotime.

• 稀土族的一种软质、银色的金属元素，同位素能发出X光射线用于小型便携式X光照射仪，存在于独居石和磷钇矿。