Word
atom
US/ˈætəm/
UK/ˈætəm/
Definitions
01chemical unit
B1 · Intermediate Countable noun Science
n. the smallest part of a chemical element that can exist.
n. the basic unit of a chemical element, consisting of a nucleus of protons and neutrons typically surrounded by electrons.
“A water molecule is made of two hydrogen atoms and one oxygen atom.”
“The researchers used a scanning tunneling microscope to manipulate individual atoms on the surface of the silicon crystal.”
02smallest unit of something
C1 · Advanced Countable noun Academic
n. the smallest possible piece or unit of an idea or a system.
n. the smallest, indivisible constituent part or unit of a larger conceptual or physical system.
“In this theory, the individual person is the atom of society.”
“Logical atomism suggests that the world consists of ultimate facts that cannot be further decomposed into simpler components.”
03a tiny amount
C2 · Proficiency Countable noun Literary
n. a very small amount of something.
n. an extremely small or negligible quantity of a quality or substance.
“There was not an atom of truth in the rumors spreading through the village.”
“He faced the accusations with dignity, showing not an atom of fear even as the verdict was read aloud.”
04programming/math
C1 · Advanced Countable noun Computing Technical
n. a single value or symbol that cannot be broken into a list.
n. a primitive value or a scalar that is not a collection; in some languages, a unique integer representing a string.
“In the Lisp programming language, an atom is a basic element like a number or a symbol.”
“The function is designed to process each atom within the nested list structure recursively until it reaches the base case.”
Antonyms
Real-World Examples
“An atom is the basic building block of chemistry.” “Atoms are the building blocks of matter.” “Atoms are the building blocks of all matter and are made up of a nucleus and a number of orbiting electrons.” Etymology
From Middle English attome, from Middle French athome, from Latin atomus (“smallest particle”), from Ancient Greek ἄτομος (átomos, “indivisible”), from ἀ- (a-, “not”) + τέμνω (témnō, “to cut”, o-grade in τομ-) + -ος (-os). Atoms are so named because they were historically thought up as to be the smallest unit of matter, and thus indivisible. Doublet of atomus.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.
Synonyms
Word family
NOUN
ADJECTIVE
Related words
Domains
- Exam level
- CambridgeCambridgeCambridge English QualificationsThe exam suite from Cambridge University Press & Assessment, from A1 Movers up to C2 Proficiency. The benchmark names double as CEFR labels.B1 PreliminaryIELTSIELTSInternational English Language Testing SystemThe 0–9 band test co-owned by the British Council, IDP, and Cambridge. Used for university entry, work, and migration.4.0–5.0TOEFL iBTTOEFL iBTTest of English as a Foreign Language, Internet-Based TestETS's academic English test, the standard route for US university admissions. Scored 0–120, with a 1–6 scale since 2026.1–6 scale: 3.0–3.544–71TOEICTOEICTest of English for International CommunicationETS's workplace English test, big in Japan and Korea. Listening & Reading scores 10–990 and tops out at C1.550–784
- Frequency
- Frequent
- Level
- B1 · Intermediate
- Updated
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