Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English


English definition of “oxygen”


noun [U]     /ˈɒk.sɪ.dʒən/ US  /ˈɑːk-/ (symbol O)
B2 a chemical element that is a gas with no smell or colour . Oxygen forms a large part of the air on Earth , and is needed by animals and plants to live .Chemical elements
(Definition of oxygen noun from the Cambridge Advanced Learner's Dictionary & Thesaurus © Cambridge University Press)
Focus on the pronunciation of oxygen

Definitions of “oxygen” in other dictionaries

Word of the Day

grand prix

one of a series of important international races for very fast and powerful cars

Word of the Day


Read our blog about how the English language behaves.

Learn More

New Words

Find words and meanings that have just started to be used in English, and let us know what you think of them.

Learn More