noun The chemical element (symbol O) with an atomic number of 8 and relative atomic mass of 15.9994. It is a colorless and odorless gas. Sometimes called elemental oxygen to distinguish it from molecular oxygen.
By molar fraction, calcium oxide contains equal parts calcium and oxygen.
noun Molecular oxygen (O2), a colorless, odorless gas at room temperature.
About 21% of the air you breathe is oxygen.
noun A mixture of oxygen and other gases, administered to a patient to help them breathe.
noun An atom of this element.
noun A condition or environment in which something can thrive.