- A gaseous element, atomic no. 8, atomic wt. 15.9994 on the basis of 12C = 12.0000; an abundant and widely distributed chemical element, which combines with most other elements to form oxides and is essential to animal and plant life.
- The molecular form of oxygen, O2, also called dioxygen.
- A medicinal gas that contains not less than 99.0%, by volume, of O2.
[G. oxys, sharp, acid and genes, forming]