: 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
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In this case, intense ultraviolet light from the supernova excites surrounding helium atoms, and these atoms then transfer energy to other elements like oxygen and nitrogen also present around the dying star.
—
Robert Lea, Space.com, 30 Oct. 2025
Fission splits the nuclei of atoms to create power while fusion causes hydrogen nuclei to collide and fuse into helium atoms that release incredible amounts of energy — essentially replicating the power of the sun.
—Rob Nikolewski, San Diego Union-Tribune, 29 Oct. 2025
These are fed through a hopper into the reactor vessel to produce a self-regulating fission reaction and are cooled by helium gas that carries off the heat to a heat exchanger to generate steam for electrical generators.
—New Atlas, 20 Oct. 2025
There is immense interest in manipulating these phase transformations and retaining superior electro-optic properties down to liquid helium temperature, according to the study published in Advanced Materials.
—Prabhat Ranjan Mishra, Interesting Engineering, 17 Oct. 2025
See All Example Sentences for helium
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Robert Lea, Space.com, 30 Oct. 2025
Fission splits the nuclei of atoms to create power while fusion causes hydrogen nuclei to collide and fuse into helium atoms that release incredible amounts of energy — essentially replicating the power of the sun.
—Rob Nikolewski, San Diego Union-Tribune, 29 Oct. 2025
These are fed through a hopper into the reactor vessel to produce a self-regulating fission reaction and are cooled by helium gas that carries off the heat to a heat exchanger to generate steam for electrical generators.
—New Atlas, 20 Oct. 2025
There is immense interest in manipulating these phase transformations and retaining superior electro-optic properties down to liquid helium temperature, according to the study published in Advanced Materials.
—Prabhat Ranjan Mishra, Interesting Engineering, 17 Oct. 2025
See All Example Sentences for helium
Cite this Entry
“Helium.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/helium. Accessed 13 Nov. 2025.
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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
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