Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “atom”

atom

noun [C]    /ˈæt̬·əm/
physics the smallest unit of any chemical element, consisting of a positive nucleus surrounded by negative electrons. Atoms can combine to form a molecule.
(Definition of atom noun from the Cambridge Academic Content Dictionary © Cambridge University Press)
Focus on the pronunciation of atom

More American English definitions for “atom”

Definitions of “atom” in other dictionaries

Word of the Day

neighbourly

friendly or helpful

Word of the Day

Blog

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