helium
n. uncountablen. a very light gas that has no color or smell. It is used to fill balloons to make them float and is also found in the sun and stars.
n. a colorless, odorless, and tasteless chemical element that is the second lightest and second most abundant in the universe. It belongs to the noble gas group and remains gaseous except under extreme conditions.
The party balloons are filled with helium so they float.
Scientists use liquid helium to cool the superconducting magnets in MRI machines to extremely low temperatures.
As a byproduct of the fusion process within stars, helium represents a significant portion of cosmic matter, though it remains relatively scarce in the Earth's atmosphere due to its low density.
From New Latin helium, from Ancient Greek ἥλιος (hḗlios, “sun”) (because its presence was first theorised in the Sun's atmosphere) with the suffix + -ium. Probably coined by Norman Lockyer. This suffix is unusual, because it is usually used only for metallic elements. It is likely that Lockyer, being an astronomer, was unaware of the usual chemical conventions.
Uncountable when referring to the element or gas in general; occasionally countable in technical contexts when referring to different isotopes.