helium

noun

he·​li·​um ˈhē-lē-əm 

ˈhēl-yəm

: a chemical element of the noble gas group with atomic number 2 that is found especially in natural gases and used chiefly for inflating airships and balloons, as a coolant for superconductors, and as a component of inert atmospheres (as in welding)

—often used before another noun

helium balloons

helium gas

see Chemical Elements Table

Examples of helium in a Sentence

Recent Examples on the Web

The pebbles are fed into the reactor via a hopper and, as the nuclear chain reaction proceeds, are cooled by helium gas to an operating temperature of 750 °C (1,382 °F). —David Szondy february 21, New Atlas, 21 Feb. 2026

In a blog post Saturday, NASA said that engineers had detected an interruption in the flow of helium in the upper stage of the Space Launch System (SLS) rocket. —Claire Cameron, Scientific American, 21 Feb. 2026

This helium issue has nothing to do with the hydrogen fuel leaks that marred a countdown dress rehearsal of the Space Launch System rocket earlier this month and forced a repeat test. —Marcia Dunn, Chicago Tribune, 21 Feb. 2026

Everything worked fine with the rocket’s helium system during both dress rehearsals, Isaacman said. —Marcia Dunn, The Orlando Sentinel, 21 Feb. 2026

Word History

Etymology

New Latin, from Greek hēlios

First Known Use

1871, in the meaning defined above

Rhymes for helium

• cilium

Kids Definition

helium

noun

he·​li·​um ˈhē-lē-əm 

: a light colorless nonflammable element that is found in various natural gases and is used especially to blow up balloons see element

Medical Definition

helium

noun

he·​li·​um ˈhē-lē-əm 

: a light colorless nonflammable gaseous element found especially in natural gases and used chiefly for inflating airships and balloons, for filling incandescent lamps, and for cryogenic research

—symbol He see Chemical Elements Table