Cambridge Dictionaries online Cambridge Dictionaries online

The most popular online dictionary and thesaurus for learners of English

English definition of “atom”


noun [C] uk   /ˈæt.əm/ us    /ˈæt̬-/
B2 the smallest unit of any chemical element, consisting of a positive nucleus surrounded by negative electrons. Atoms can combine to form a molecule: A molecule of carbon dioxide (CO2) has one carbon atom and two oxygen atoms.figurative He hasn't an atom of sense (= he has no sense), that boy.
(Definition of atom from the Cambridge Advanced Learners Dictionary & Thesaurus © Cambridge University Press)
What is the pronunciation of atom?
Add Cambridge dictionaries to your browser to your website

More meanings of “atom”

Definitions of “atom” in other dictionaries

Word of the Day

bright spark

a person who is intelligent, and full of energy and enthusiasm

Word of the Day

Highly delighted, bitterly disappointed, ridiculously cheap: adverbs for emphasis.

by Liz Walter,
October 22, 2014
We often make adjectives stronger by putting an adverb in front of them. The most common ones are very and, for a stronger meaning, extremely: He was very pleased. The ship is extremely large. However, we don’t use very or extremely for adjectives that already have a strong meaning, for example fantastic,

Read More 

life tracking noun

October 20, 2014
the use of one or more devices or apps to monitor health, exercise, how time is spent, etc.

Read More