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

Ryzhikov worked on the Russian segment's Elektron oxygen generator and Zubritskiy swapped out ventilation dust filters. —Robert Z. Pearlman, Space.com, 28 June 2025

Nine out of 34 oxygen stations are partially operational, and blood banks are nearly empty, according to the ministry. —Diaa Ostaz, ABC News, 28 June 2025

My wife uses the same oxygen bleach when doing the laundry. —Tim Carter, Hartford Courant, 28 June 2025

For fire to exist, three elements are needed: fuel, heat, and oxygen. —Discover Magazine, 27 June 2025

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