| Word | Definitions | Synonyms |
|---|---|---|
| oxygen | (noun) a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust | Synonyms: atomic number 8, O |
| oxygenase | (noun) an oxidoreductase that catalyzes the incorporation of molecular oxygen | - |
| oxygenation | (noun) the process of providing or combining or treating with oxygen | - |