(physics) Any of several series of spectral lines of hydrogen that correspond to quantum transitions between the various allowed energy levels of the hydrogen atom.

(inorganic chemistry, countable) Synonym of bicarbonate / (inorganic chemistry, uncountable) carbonic acid

(physics) all the lines in the emission or absorption spectrum of hydrogen; each one corresponding to an allowed transition between quantum energy levels

A service station for hydrogen vehicles.

a small thermonuclear device in the warhead of a missile

(obsolete, chemistry) phosphine

Any vehicle that uses hydrogen as its principal fuel, normally via the electricity produced by a fuel cell.

(obsolete, chemistry) hydrogen sulphide

(chemistry, obsolete) hydrogen selenide

(obsolete, chemistry) Hydrogen telluride.