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[hee-lee-uh m] /ˈhi li əm/
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. Symbol: He; atomic weight: 4.0026; atomic number: 2; density: 0.1785 g/l at 0°C and 760 mm pressure.
Origin of helium
1875-80; < New Latin < Greek hḗli(os) the sun + New Latin -ium -ium

helium I

colorless liquid helium existing below its boiling point of 4.2 K and above the lambda point of 2.186 K.

helium II

liquid helium existing as a superfluid below the lambda point of 2.186 K, having very low viscosity and very high thermal conductivity. Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for helium
  • The latest feat leaves helium and neon as the only stable elements refusing to join in a compound.
  • Another advantage of the pebble-bed reactor is the helium coolant.
  • Based on their densities, four of the planets appear to have thick atmospheres of hydrogen and helium.
  • Conventional wisdom holds that the first stars were born of the hydrogen and helium present in the early universe.
  • helium is helium, even if you're inhaling it along with oxygen to help you breath better when you're sick.
  • Liquid nitrogen is far cheaper and easier to handle than liquid helium.
  • He has used helium beams this way to create cantilevers hinged at one end.
  • His team has replaced the first stage with a gigantic reusable helium balloon.
  • And to make ultra-heavy hydrogen, they replaced one of the electrons in a helium atom with a negative muon.
  • If the giant blimps can get the helium and helium containers they need to fly, that is.
British Dictionary definitions for helium


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
Word Origin
C19: New Latin, from helio- + -ium; named from its having first been detected in the solar spectrum
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for helium

1868, coined from Greek helios "sun" (see sol), because the element was detected in the solar spectrum during the eclipse of Aug. 18, 1868, by English astronomer Sir Joseph N. Lockyer (1836-1920) and English chemist Sir Edward Frankland (1825-1899). It was not actually obtained until 1895; it was assumed before that to be an alkali metal, hence the ending in -ium.

Online Etymology Dictionary, © 2010 Douglas Harper
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helium in Medicine

helium he·li·um (hē'lē-əm)
Symbol He
An inert gaseous element occurring in natural gas and used as a component of artificial atmospheres and laser media. Atomic number 2; atomic weight 4.0026; boiling point -268.9°C; density at 0°C 0.1785 gram per liter.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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helium in Science
Symbol He
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. See Periodic Table.

Our Living Language  : 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.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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helium in Culture

helium definition

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.

Note: Helium is the best known of the inert gases.
Note: Because it is lighter than air, helium is used to fill balloons.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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