Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “co-”


prefix    /koʊ/
together; with: co-author co-founder They were named co-winners of the player of the week award.
(Definition of co- prefix from the Cambridge Academic Content Dictionary © Cambridge University Press)
Focus on the pronunciation of co-

Definitions of “co-” in other dictionaries

Word of the Day


a person or group who receives money, advantages, etc. as a result of something else

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