Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “un-”


prefix uk   /ʌn-/ us  
used to add the meaning 'not', 'lacking', or 'the opposite of' before adjectives, adverbs, verbs, and nouns: unrealistic unhappily unscrew unfairnessYes, no and notLacking thingsScarce, inadequate and not enoughEssential or necessary
(Definition of un- prefix from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
What is the pronunciation of un-?
Browse related topics

You are looking at an entry to do with Lacking things, but you might be interested in these topics from the Wanting topic area:

Add Cambridge dictionaries to your browser to your website

Definitions of “un-” in other dictionaries

Word of the Day


like hops (= dried fruit used to make beer)

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