thulium
/ˈθuːliəm/
noun
- A soft, silvery-gray metal that is a chemical element. It is used in some lasers and in portable X-ray machines.
- Thulium is one of the rarest elements found in the Earth's crust.
- Scientists use thulium in small medical devices for imaging.
- The laser contained a small amount of thulium to produce a specific wavelength of light.