oxygen ox·y·gen (ŏk'sĭ-jən)
An element constituting 21 percent of the atmosphere by volume that occurs as a diatomic gas, O2, combines with most elements, is essential for plant and animal respiration, and is required for nearly all combustion. Atomic number 8; atomic weight 15.9994; melting point -218.8°C; boiling point -183.0°C; gas density at 0°C 1.429 grams per liter; valence 2.
A medicinal gas containing not less than 99.0 percent, by volume, of O2.
Dictionary.com presents 366 FAQs, incorporating some of the frequently asked questions from the past with newer queries.