plural of helium

(uncountable) The second lightest chemical element (symbol He) with an atomic number of 2 and atomic weight of 4.002602, a colorless, odorless and inert noble gas.

(technical diving, saturation diving, underwater diving) Synonym of helium descrambler

(technical diving, saturation diving, underwater diving) An electronic device that lowers the pitch of speech, to compensate for the high-pitched speech of someone breathing in a helium atmosphere breathing mix (ie. heliox, heliair, ...), so as to be understandable to other people.

(inorganic chemistry) Ellipsis of helium hydride cation. The unstable binary cation HeH⁺ present in interstellar space. It is the strongest acid, reactive with every chemical species except positive ions, including electrons.

(physics, astronomy) the nucleosynthesis process, in stars with temperatures over 10⁸K, in which helium is converted to carbon and then to oxygen, neon and magnesium

(astronomy) A star in which the strength of the helium absorption lines vary periodically; at times appearing to be a helium star.

(physics) nuclear fusion involving helium nuclei.

Speech whose timbre (but not pitch) has been affected by the inhalation of helium, due to the difference in the speed of sound in that gas, compared with air.

(astronomy) The sudden beginning of the burning of helium in the core of stars of intermediate mass or on the surface of an accreting white dwarf.