/ ˈɒksɪdʒən; NAmE ˈɑːk-/ noun
[ U ] ( symb O ) a chemical element. Oxygen is a gas that is present in air and water and is necessary for people, animals and plants to live.
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WORD ORIGIN
late 18th cent.: from French (principe) oxygène acidifying constituent (because at first it was held to be the essential component in the formation of acids).