Hȳ'dro-gen, n.

n. [Fr. hydrogène, from Gr. ὕδωρ, water, and γενεῖν, to beget, generate; so called as being considered the generator of water.] (Chem.) A gas which constitutes one of the elements of water, of which it forms one ninth, and oxygen eight ninths. It is an inflammable, colorless gas, of extreme lightness. Its specific gravity is 0.0692; that of water being 1. It enters as an element into the composition of nearly all organic bodies. In consequence of its extreme lightness, it is often employed for filling air-balloons.