hydrogen
hydro·gen BrE [ˈhaɪdrədʒən] NAmE [ˈhaɪdrədʒən] noun uncountable (symb. H) a chemical element. Hydrogen is a gas that is the lightest of all the elements. It combines with ↑oxygen to form water. Word Origin: [hydrogen] late 18th cent.: coined in French from Greek hudro- ‘water’ + -genēs ‘-born, of a specified kind’, from gen- (root of gignomai ‘be born, become’, genos ‘a kind’).
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