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[ok-si-juh n] /ˈɒk sɪ dʒən/
noun, Chemistry.
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.
Origin of oxygen
1780-90; < French oxygène, equivalent to oxy- oxy-1 + -gène -gen
Related forms
[ok-si-jen-ik] /ˌɒk sɪˈdʒɛn ɪk/ (Show IPA),
[ok-sij-uh-nuh s] /ɒkˈsɪdʒ ə nəs/ (Show IPA),
[ok-si-juh-nis-i-tee] /ˌɒk sɪ dʒəˈnɪs ɪ ti/ (Show IPA),
noun Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2018.
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British Dictionary definitions for oxygen


  1. a colourless odourless highly reactive gaseous element: the most abundant element in the earth's crust (49.2 per cent). It is essential for aerobic respiration and almost all combustion and is widely used in industry. Symbol: O; atomic no: 8; atomic wt: 15.9994; valency: 2; density: 1.429 kg/m³; melting pt: –218.79°C; boiling pt: –182.97°C
  2. (as modifier): an oxygen mask
Derived Forms
oxygenic (ˌɒksɪˈdʒɛnɪk), oxygenous (ɒkˈsɪdʒɪnəs) adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for oxygen

gaseous chemical element, 1790, from French oxygène, coined in 1777 by French chemist Antoine-Laurent Lavoisier (1743-1794), from Greek oxys "sharp, acid" (see acrid) + French -gène "something that produces" (from Greek -genes "formation, creation;" see -gen).

Intended to mean "acidifying (principle)," it was a Greeking of French principe acidifiant. So called because oxygen was then considered essential in the formation of acids (it is now known not to be). The element was isolated by Priestley (1774), who, using the old model of chemistry, called it dephlogisticated air. The downfall of the phlogiston theory required a new name, which Lavoisier provided.

Online Etymology Dictionary, © 2010 Douglas Harper
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oxygen in Medicine

oxygen ox·y·gen (ŏk'sĭ-jən)
Symbol O

  1. 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.

  2. A medicinal gas containing not less than 99.0 percent, by volume, of O2.

The American Heritage® Stedman's Medical Dictionary
Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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oxygen in Science
Symbol O
A nonmetallic element that exists in its free form as a colorless, odorless gas and makes up about 21 percent of the Earth's atmosphere. It is the most abundant element in the Earth's crust and occurs in many compounds, including water, carbon dioxide, and iron ore. Oxygen combines with most elements, is required for combustion, and is essential for life in most organisms. 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 Periodic Table.

Our Living Language  : In 1786, the French chemist Antoine Lavoisier coined a term for the element oxygen (oxygène in French). He used Greek words for the coinage: oxy- means "sharp," and -gen means "producing." Oxygen was called the "sharp-producing" element because it was thought to be essential for making acids. Lavoisier also coined the name of the element hydrogen, the "water-producing" element, in 1788. Soon after, in 1791, another French chemist, J. A. Chaptal, introduced the word nitrogen, the "niter-producing" element, referring to its discovery from an analysis of nitric acid.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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oxygen in Culture

oxygen definition

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.
The New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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