hydr(o)-²

Hydrogen

>Greek hudōr, hudro‑, water.

Hydrogen is the ‘water maker’ because it produces water when burned in air or oxygen; hydrochloric acid is a strongly acidic solution of the gas hydrogen chloride in water; the hydroxonium ion is H₃O⁺, the hydrated hydrogen ion. A hydrocarbon is a compound of hydrogen and carbon; a hydride is a binary compound of hydrogen with a metal; hydrazine (hydro‑ plus azo‑ and ‑ine³) is a fuming liquid often used as a rocket fuel; hydrogenation is the chemical addition of hydrogen to a substance. See also dehydro‑.