Helium is a very light gas that will not burn. A helium balloon, filled with helium, liquid helium.
It is the second lightest element and completely inert, which is why airships use it instead of hydrogen. It is also the only element discovered in space before it was found on earth — spotted in the sun's spectrum in 1868. Liquid helium is what cools MRI scanners, and the world supply is genuinely limited, so party balloons are a slightly awkward use of it. Note that inhaling it raises the pitch of a voice.
1nounheliumA very light inert gas.
“The balloons were filled with helium, so they floated up to the ceiling.”
helium is a chemical element.
The name is from Greek helios, the sun, because it was first identified in the sun's spectrum. The -ium ending normally marks a metal, which is why helium's name is a small anomaly.
Ancient Greek
ἥλιος — sun
New Latin
helium
English, today
helium
From New Latin helium, from Ancient Greek ἥλιος (“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.
Etymology from Wiktionary, CC BY-SA