oxygen

American  

[ok-si-juhn] / ˈɒk sɪ dʒən /

noun

Chemistry.

• oxygens
  plural

1. 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. O; 15.9994; 8; density: 1.4290 grams/liter at 0°C and 760 millimeter pressure.

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oxygen British  

/ ˈɒksɪdʒən /

noun

1. 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

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oxygen Scientific  

/ ŏk′sĭ-jən /

1. 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 −218.8°C; boiling point −182.9°C; gas density at 0°C 1.429 grams per liter; valence 2.

2. See Periodic Table

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oxygen Cultural  

1. 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.

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Word History

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.

Discover More

Oxygen is a waste product of green plants and photosynthesis.

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.)

Other Word Forms

Derived Forms

• oxygenicity
  noun
• oxygenic
  adjective
• oxygenous
  adjective

Inflected Forms

Nouns

• oxygens
  plural

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Etymology

Origin of oxygen

First recorded in 1780–90; from French oxygène, equivalent to oxy- + -gène; see origin at oxy- ¹, -gen

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Explanation

Oxygen is air, the stuff we breathe, the thing that makes our lives possible. It is an element, a basic chemical found on the earth. In fact, we don't breathe pure oxygen; our air is about 20 percent oxygen. Still, oxygen is everywhere—it’s the third most common element on earth. Usually, the word is used in scientific contexts. Still, when someone has a big personality and likes to be the center of attention, we say, they "take all the oxygen out of the room." That means they are a blowhard and attention hog. If they really took your oxygen, you’d be dead.

Example Sentences

See Examples For:

oxygen oxygens

The meeting of water and plastic creates a third class of molecules called reactive oxygen species.

From Los Angeles Times ● Oct. 17, 2026

From creating oxygen to fertilizing the soil, leaves make possible human life on earth.

From The Wall Street Journal ● Oct. 16, 2026

"We do not just send smoke... The oxygen in Singapore and Malaysia also comes from our forests," said Syahganda Nainggolan in a video that swiftly went viral and prompted furious responses.

From Barron's ● Oct. 16, 2026

The cause was determined to be a lack of oxygen to the brain due to severe asthma with acute lung injury while fighting cold-like symptoms.

From Los Angeles Times ● Oct. 14, 2026

Arletta invited a nurse, a doctor, and one ninety-five-year-old lady in an oxygen mask onto the stage, and they crafted and chatted behind a big white table.

From "Hope Springs" by Jaime Berry

"Those two oxygens greatly limit the window of opportunity that you have in terms of doing chemical transformations," Movassaghi says.

From Science Daily ● Dec. 22, 2025

Zeolites can trap copper, iron and other metals that can act as catalysts to replace methane's four hydrogen atoms with two oxygens.

From Scientific American ● Jul. 31, 2019

The oxygens were then free to link with iron, creating vast rust-colored deposits of iron oxide across our planet's surface.

From Science Magazine ● Jan. 10, 2019

They are built with a three-dimensional framework of silica tetrahedra in which all four corner oxygens are shared with adjacent tetrahedra.

From Textbooks ● Jan. 1, 2017

The mass spectrometer then works out how many carbons there are in the molecule, how many hydrogens, how many oxygens; and starts to build up the complete structure.

From BBC ● Jul. 7, 2015

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