oxygen
noun
ox·y·gen
ˈäk-si-jən 
1
: a chemical element with atomic number 8 that constitutes 21 percent of the Earth's atmosphere, that is capable of combining with all elements except some noble gases, that is active in physiological processes of almost all known organisms, and that is involved especially in combustion
—often used before another noun
oxygen tanks
an oxygen mask
see Chemical Elements Table
2
: something that sustains or fuels
Disagreement is the true oxygen of these magazines …—
Joseph Epstein
Joseph EpsteinExamples of oxygen in a Sentence
Recent Examples on the Web
Supportive care can include things like oxygen, mechanical ventilation, extracorporeal membrane oxygenation, intravenous fluids, medications to support blood pressure and flow and dialysis depending on the situation.
—Bruce Y. Lee, Forbes.com, 18 May 2026
Recovery teams explored two of the three chambers on Friday, but the search was limited due to considerations over oxygen and decompression.
—CBS News, 18 May 2026
Each event disrupts sleep architecture and drops oxygen levels, leaving people exhausted, foggy and at higher long-term risk for cardiovascular disease.
—Allison Palmer, Sacbee.com, 18 May 2026
Röösli noted that the injector, one of the most critical parts of the propulsion unit, had to precisely mix propane and liquid oxygen, and prevent destructive pressure waves from traveling backward into the supply lines.
—Georgina Jedikovska, Interesting Engineering, 18 May 2026
See All Example Sentences for oxygen
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Bruce Y. Lee, Forbes.com, 18 May 2026
Recovery teams explored two of the three chambers on Friday, but the search was limited due to considerations over oxygen and decompression.
—CBS News, 18 May 2026
Each event disrupts sleep architecture and drops oxygen levels, leaving people exhausted, foggy and at higher long-term risk for cardiovascular disease.
—Allison Palmer, Sacbee.com, 18 May 2026
Röösli noted that the injector, one of the most critical parts of the propulsion unit, had to precisely mix propane and liquid oxygen, and prevent destructive pressure waves from traveling backward into the supply lines.
—Georgina Jedikovska, Interesting Engineering, 18 May 2026
See All Example Sentences for oxygen
Cite this Entry
“Oxygen.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/oxygen. Accessed 21 May. 2026.
Copy CitationKids Definition
oxygen
noun
ox·y·gen
ˈäk-si-jən
: a reactive element that is found in water, rocks, and free as a colorless tasteless odorless gas which forms about 21 percent of the atmosphere, that is capable of combining with almost all elements, and that is necessary for life see element
Etymology
from French oxygène "oxygen," literally, "acid producer," from oxy- "sharp, acid" (from Greek oxys "sharp, sour") and -gène "one that produces or generates" (from Greek -genēs "born, generated")
Word Origin
Oxygen was discovered by two scientists working independently, Joseph Priestley of England and Carl Scheele of Sweden. However, it was the French chemist Antoine Lavoisier who later gave the gas its name. He said the most common characteristic of this element was its ability to combine with other substances to form acids. For this reason Lavoisier named it oxygène, literally meaning "acid producer." The origin of his word was two Greek elements, oxys, meaning "sharp, sour," and -genēs, meaning "born, generated."
Medical Definition
oxygen
noun
ox·y·gen
ˈäk-si-jən
: a colorless tasteless odorless gaseous element that constitutes 21 percent of the atmosphere and is found in water, in most rocks and minerals, and in numerous organic compounds, that is capable of combining with all elements except the inert gases, that is active in physiological processes, and that is involved especially in combustion processes
—symbol O
see Chemical Elements Table
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