- a chemical element. Hydrogen is a gas that is the lightest of all the elements. It combines with oxygen to form water.Topics Physics and chemistryc1Oxford Collocations DictionaryHydrogen is used before these nouns:
- bomb
- fuel
- gas
- …
Word Originlate 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’).Definitions on the go
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hydrogen