helium

[ hee-lee-uh m ]
/ ˈhi li əm /

noun

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

Definition for helium (2 of 3)

helium I

noun

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

Definition for helium (3 of 3)

helium II

noun

liquid helium existing as a superfluid below the lambda point of 2.186 K, having very low viscosity and very high thermal conductivity.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for helium

British Dictionary definitions for helium

helium
/ (ˈhiːlɪəm) /

noun

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°CSee also alpha particle

Word Origin for helium

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

Medicine definitions for helium

helium
[ hēlē-əm ]

n. Symbol He

An inert gaseous element used in liquid form as a cryogen and as a substitute for nitrogen in artificial breathing mixtures for deep-sea diving and workers in high-pressure conditions. Atomic number 2.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Science definitions for helium

helium
[ hēlē-əm ]

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.

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Culture definitions for helium

helium

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.

notes for helium

Helium is the best known of the inert gases.

notes for helium

Because it is lighter than air, helium is used to fill balloons.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.