Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “quantum”


noun [C] uk   /ˈkwɒn.təm/ us    /ˈkwɑːn.t̬əm/ (plural quanta) specialized
the smallest amount or unit of something, especially energy: quantum theoryParticular theories and concepts in physicsWeighing and measuring
(Definition of quantum from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
What is the pronunciation of quantum?
Add Cambridge dictionaries to your browser to your website

Definitions of “quantum” in other dictionaries

Word of the Day


to send something through the air with force, especially by a sudden movement of the arm

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