helium
/ˈhiːlɪəm/noun
mass noun
- the chemical element of atomic number 2, an inert gas which is the lightest member of the noble gas series. (Symbol: He).氦（符号： 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℃） 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.
词源
late 19th cent.: modern Latin, from Greek hēlios 'sun', because its existence was inferred from an emission line in the sun's spectrum.