helium

American  

[hee-lee-uhm] / ˈhi li əm /

noun

1. an inert, gaseous element present in the sun's atmosphere and in natural gas, and also occurring as a radioactive decomposition product, used as a substitute for flammable gases in dirigible balloons. He; 4.0026; 2; density: 0.1785 grams/liter at 0°C and 760 millimeters pressure.

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helium British  

/ ˈhiːlɪəm /

noun

1. a very light nonflammable colourless odourless element that is an inert gas, occurring in certain natural gases: used in balloons and in cryogenic research. Symbol: He; atomic no: 2; atomic wt: 4.002602; density: 0.1785 kg/m³; at normal pressures it is liquid down to absolute zero; melting pt: below –272.2°C; boiling pt: –268.90°C See also alpha particle

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helium Scientific  

/ hē′lē-əm /

1. A very lightweight, colorless, odorless element in the noble gas group. Helium occurs in natural gas, in radioactive ores, and in small amounts in the atmosphere. It has the lowest boiling point of any substance and is the second most abundant element in the universe. Helium is used to provide lift for balloons and blimps and to create artificial air that will not react chemically. Atomic number 2; atomic weight 4.0026; boiling point −268.9°C; density at 0°C 0.1785 gram per liter.

2. See Periodic Table

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helium Cultural  

1. A chemical element, usually found in the form of a gas, in which two electrons are in orbit, and the nucleus consists of two protons and two neutrons. Its symbol is He.

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Word History

The second most abundant element in the universe after hydrogen, Helium (symbol He) is a colorless, odorless, nonmetallic gas that is produced abundantly by the nuclear fusion in all stars and is found in smaller amounts on Earth. It was discovered by the British scientist—and founding editor of the journal Nature—Joseph Norman Lockyer in 1868, while he was studying a solar eclipse with a spectroscope, an instrument that breaks light up into a spectrum. If an element is heated up enough to glow, the emitted light produces a unique spectrum when refracted through a prism. Lockyer noticed that the spectrum of the Sun's corona, which is visible only during a solar eclipse, contained lines produced by an unknown element. He named the element helium from helios, the Greek word for “sun.” Helios gives us many other words pertaining to the Sun, such as heliocentric and perihelion.

Discover More

Because it is lighter than air, helium is used to fill balloons.

Helium is the best known of the inert gases.

Etymology

Origin of helium

First recorded in 1875–80; from New Latin, from Greek hḗli(os) “the sun” + New Latin -ium noun suffix; see -ium

Explanation

The element helium is a colorless, odorless gas. Because helium is lighter than air, it's commonly used for filling balloons to make them float. Because of the effect that helium has when lightweight objects are filled with it — making party balloons and parade floats hover in the air as if by magic — it's one of the best-known elements. Helium is almost always a gas, unless it's subjected to very extreme conditions, and it's been used at various times in military airships and weather balloons. The word helium comes from a Greek root, helios, or "sun," because it was initially discovered in the sun's spectrum.

Example Sentences

Helium is the second-most-common element in the universe after hydrogen, but it is rare on Earth, where it mainly exists in small concentrations in pockets of natural gas.

From The Wall Street Journal • Mar. 31, 2026

Helium 3 alone currently trades at more than $20,000 per kilogram, making it one of the most valuable resources on earth.

From BBC • Mar. 31, 2026

Helium plays a crucial role in chip making, and Qatar is a key producer, with over a third of 2024 global production, according to the U.S.

From Barron's • Mar. 13, 2026

Helium is used in the manufacture of semiconductors.

From MarketWatch • Mar. 13, 2026

I won the hand of the lovely Dejah Thoris, Princess of Helium.

From "Cosmos" by Carl Sagan