1. A nonmetallic bivalent element that is normally a colourless, odourless, tasteless, nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust
   "Oxygen is essential for human respiration"; "Oxygen, atomic number 8, is essential for cellular respiration";
   - O, atomic number 8

Derived forms: oxygens

Type of: chemical element, element, gas

Part of: air, H2O, ozone, water

Encyclopedia: Oxygen, 8O