oxygen

noun5

1. •
   the gas that makes fire burn and that living things take in when they breathe

   • By molar fraction, calcium oxide contains equal parts calcium and oxygen.
2. •
   Molecular oxygen (O₂), a colorless, odorless gas at room temperature.

   • About 21% of the air you breathe is oxygen.
3. •
   A mixture of oxygen and other gases, administered to a patient to help them breathe.
4. •
   An atom of this element.

   • Look first at any structure to see if there is a carbon with two oxygens attached. Hemiacetals, hemiketals, acetals, and ketals are all alike in that regard. — 2013
5. •
   (figurative) A condition or environment in which something can thrive.

   • Silence is the oxygen of shame.
   • They hoped to starve the terrorists of the oxygen of publicity.