helium
Pronunciation: /ˈhiːlɪəm/
noun
- the chemical element of atomic number 2, an inert gas which is the lightest member of the noble gas series. (Symbol: He)
- Helium occurs in traces in air, and more abundantly in natural gas deposits. It is used as a lifting gas for balloons and airships, and liquid helium (boiling point: 4.2 kelvins, −268.9°C) is used as a coolant. Helium is produced in stars as the main product of the thermonuclear fusion of hydrogen, and is the second most abundant element in the universe after hydrogen
Origin:
late 19th century: modern Latin, from Greek hēlios 'sun', because its existence was inferred from an emission line in the sun's spectrum