Definition of helium in US English:

helium

noun

  • The chemical element of atomic number 2, an inert gas which is the lightest member of the noble gas series.

    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

    • ‘Ramsay realized that argon and helium might be members of a hitherto unsuspected new group in the Periodic Table.’
    • ‘Over the next few years many types of laser were built, some using a mixture of helium and neon, others carbon dioxide or organic dyes.’
    • ‘They were the ones who were always crying and throwing fits when they lost their helium balloons.’
    • ‘Does it contain yet more unknown chemical elements, like helium?’
    • ‘Because it is chemically inert, helium was not identified on Earth until some time later, in 1895.’
    • ‘In composition it resembles a small star, with helium and hydrogen as the main gases.’
    • ‘During the last years of his life he worked steadily on the wave mechanics of the hydrogen and helium atom.’
    • ‘In practice air is nowadays never used in deep diving, the nitrogen being replaced by helium, which is far less soluble in fat.’
    • ‘When most of the hydrogen is fused into helium, fusion stops and and gravity again takes over.’
    • ‘Eventually, there will not be any hydrogen left in the center of the Sun to make helium.’
    • ‘The atomic elements heavier than hydrogen and helium could not have been produced during the inferno of the Big Bang.’
    • ‘Even though helium is twice as dense as hydrogen, this is less than one metric ton of gas.’
    • ‘However, if a proton is added to the hydrogen atom, a new element, helium is created.’
    • ‘Argon is denser than air, and certainly helium, which means that it has more molecules to retain heat.’
    • ‘There he worked with Born on atomic theory, writing a joint paper with him on helium.’
    • ‘At launch, the balloon is partially inflated with helium and expands as it rises.’
    • ‘Other light elements that are commonly proposed for the outer core are silicon, carbon, helium, and nitrogen.’
    • ‘Today, balloons in Japan are lifted by hot air rather than the more expensive helium or hydrogen.’
    • ‘During the history of our universe, more helium was made because the process that drives the stars turns hydrogen into helium.’
    • ‘Cool the detectors with liquid nitrogen instead of solid hydrogen or liquid helium.’

Origin

Late 19th century: modern Latin, from Greek hēlios ‘sun’, because its existence was inferred from an emission line in the sun's spectrum.

Pronunciation

helium

/ˈhēlēəm//ˈhiliəm/