Oxygen /ˈɒksɪdʒ(ə)n/ Learn to pronounce noun 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"
Oxygen is a chemical element that constitutes 21 percent of the Earth's atmosphere, that is capable of combining with all elements except some noble gases, that is active in physiological processes of almost all known organisms, and that is involved especially in combustion — see Chemical Elements Table.
