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

oxygenless

ˈäk-si-jən-ləs 

adjective

Examples of oxygen in a Sentence

Recent Examples on the Web

Then there is the matter of which stories receive oxygen and which ones are smothered with a decorative pillow. —Larry Clifton, The Orlando Sentinel, 3 May 2026

However, if there is an actual issue—such as a faulty oxygen sensor heater—clearing the code only turns off the light temporarily without fixing the problem. —Hartford Courant, 3 May 2026

If discoloration remains, repeat the oxygen bleach paste step. —Mary Marlowe Leverette, Southern Living, 3 May 2026

The science of acoustic fire suppression, which has long been known and documented in scientific literature and the press, works by vibrating oxygen molecules away from a fuel source, depriving the fire of a critical component needed for combustion. —Cyrus Farivar, ArsTechnica, 2 May 2026

Word History

Etymology

French oxygène, from Greek oxys, adjective, acidic, literally, sharp + French -gène -gen; akin to Latin acer sharp — more at edge

First Known Use

1788, in the meaning defined at sense 1

Phrases Containing oxygen

• biochemical oxygen demand
• biological oxygen demand
• oxygen cycle
• oxygen debt
• oxygen demand
• oxygen mask
• oxygen tent

Kids 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

oxygenic

ˌäk-si-ˈjen-ik 

adjective