helium

he·li·um

noun \ˈhē-lē-əm, ˈhēl-yəm\

Definition of HELIUM

: a light colorless inert gaseous element found especially in natural gases and used chiefly for inflating airships and balloons, in lamps, in cryogenic research, and as a component of inert atmospheres (as in welding) — see element table

Origin of HELIUM

New Latin, from Greek hēlios

First Known Use: 1872

he·li·um

noun \ˈhē-lē-əm\   (Medical Dictionary)

Medical Definition of HELIUM

: 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 element table

helium

noun    (Concise Encyclopedia)

Chemical element, chemical symbol He, atomic number 2. A noble gas, it is colourless, odourless, tasteless, completely unreactive, and nontoxic. First found by spectroscopy of the Sun's atmosphere in 1868, it is the second most abundant and second-lightest element in the universe (after hydrogen). Helium makes up a tiny proportion of the atmosphere but as much as 7% of natural gas. It is the product of radioactive decay (see radioactivity) and is used in helium dating. It is used as an inert gas in welding, rocket propulsion, balloon flight, hyperbaric chambers, deep-sea diving (see nitrogen narcosis), gas chromatography, luminous signs, and cryogenics. Liquid helium, which exists only below 452 °F (268.9 °C, about 4° C above absolute zero), is a “quantum fluid” (see fluid mechanics; quantum mechanics), with unique properties, including superfluidity, superconductivity, and near-zero viscosity.