Real Dictionary

helium
uncountable noun: Helium is a very light gas that is colourless and has no smell.

helium in American English
a colorless, odorless chemical element, one of the noble gases, having the lowest known boiling and melting points: it is used in low-temperature work, as a diluent for oxygen, in deep-sea breathing systems, for inflating balloons, etc.: symbol, He; at. n
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; at. wt.: 4.0026; at. no.: 2; density: 0.1785 g/ l at 0

helium in British English
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 li