[ok-si-juh
n] 
| a colorless, odorless, gaseous element constituting about one-fifth of the volume of the atmosphere and present in a combined state in nature. It is the supporter of combustion in air and was the standard of atomic, combining, and molecular weights until 1961, when carbon 12 became the new standard. Symbol: O; atomic weight: 15.9994; atomic number: 8; density: 1.4290 g/l at 0°C and 760 mm pressure. |
| ox·y·gen (ŏk'sĭ-jən) n. Symbol O A nonmetallic element constituting 21 percent of the atmosphere by volume that occurs as a diatomic gas, O2, and in many compounds such as water and iron ore. It 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 -218.4°C; boiling point -183.0°C; gas density at 0°C 1.429 grams per liter; valence 2. See Table at element. [French oxygène : Greek oxus, sharp, acid; see ak- in Indo-European roots + French -gène, -gen.] ox'y·gen'ic (-jěn'ĭk) adj., ox'y·gen'i·cal·ly adv., ox·yg'e·nous (ŏk-sĭj'ə-nəs) adj. |
An element, normally a gas, that makes up about one-fifth of the atmosphere of the Earth. Oxygen is usually found as a molecule made up of two atoms. Its symbol is O.
Note: When we breathe in oxygen, it is carried by the hemoglobin in our blood throughout the body, where it is used to generate energy by oxidation. (See respiration.)
Note: Oxygen is a waste product of green plants and photosynthesis.
oxygen ox·y·gen (ŏk'sĭ-jən)
n.
Symbol O
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.