- a colourless, odourless reactive gas, the chemical element of atomic number 8 and the life-supporting component of the air: if breathing stops, there is no oxygen getting to the brain and the cells begin to die hydrogen and carbon in the fuel combine with the oxygen in the air to form carbon dioxide and water [as modifier]:an oxygen supply (Symbol: O)
Oxygen is essential to plant and animal life and is a constituent of most organic compounds. It forms about 20 per cent of the earth’s atmosphere, and is the most abundant element in the earth’s crust, mainly in the form of oxides, silicates, and carbonates
late 18th century: from French (principe) oxygène 'acidifying constituent' (because at first it was held to be the essential component in the formation of acids)
Spell oxygen with oxy- at the beginning.