Logo
dictionary thesaurus

atom

noun
at·​om | \ ˈa-təm How to pronounce atom (audio) \

Definition of atom

1a : the smallest particle of an element that can exist either alone or in combination an atom of hydrogen
b : the atom considered as a source of vast potential constructive or destructive energy … a largely forgotten legacy of this country's conquest of the atom.— William J. Broad … when Congress passed the Atomic Energy Act in 1954 and allowed private utilities to "harness the atom."— Barry Werth
2 : a tiny particle : bit There's not an atom of truth in what he said.
3 : one of the minute indivisible particles of which according to ancient materialism (see materialism sense 1a) the universe is composed
Other Words from atom Synonyms Did You Know? More Example Sentences Learn More about atom

Keep scrolling for more

Did You Know?

Some ancient philosophers believed that matter is infinitely divisible, that any particle, no matter how small, can always be divided into smaller particles. Others believed that there must be a limit and that everything in the universe must be made up of tiny indivisible particles. Such a hypothetical particle was called atomos in Greek, which means “indivisible.” According to modern atomic theory, all matter is made up of tiny particles named atoms from the ancient Greek atomos. However, it has turned out that atoms are not indivisible after all. Indeed, the splitting of atoms can be used to produce vast amounts of energy, as in atom bombs.

Examples of atom in a Sentence

There is not an atom of truth to what he said. give me just one atom of information about the novel's surprise ending

Recent Examples on the Web

 Not long before that (cosmically speaking), the sun had burst into being, fusing together hydrogen atoms from an immense ball of gas, setting alight a fire that burns to this day. — Brian Resnick, Vox, "How Apollo moon rocks reveal the epic history of the cosmos," 15 July 2019 Light shines from the interior of a star and is absorbed by atoms in its upper layer, creating a stellar spectra. — Natalie Hinkel, The Conversation, "Accelerating exoplanet discovery using chemical fingerprints of stars," 25 June 2019 The atoms in solids, such as silicon or diamond, are relatively stationary, but their crystalline order dramatically simplifies the equations necessary to understand their properties. — James Kakalios, WSJ, "‘Liquid Rules’ Review: Going With the Flow," 7 Mar. 2019 Go is complex — there are more possible board positions than atoms in the universe — and the best players win not with sheer calculation, but through intuition. — New York Times, "Mark Zuckerberg, Elon Musk and the Feud Over Killer Robots," 9 June 2018 Organometallic compounds are substances that have a metal bonding with at least one carbon atom of an organic molecule. — Ranjit Devraj, Quartz India, "Mango leaves: Indian scientists’ solution to a $2.5 trillion global shipping problem," 24 July 2019 To put it in perspective, a gravitational wave detector measures changes that are far smaller than the diameter of an atom and are more like the diameter of a single proton. — Chris Lee, Ars Technica, "Satellites play chase to measure gravity, achieve picometer accuracy," 23 July 2019 On the other side of the battery, the manganese oxide gains an oxygen atom from the water and leaves hydroxide ions behind to balance out the hydroxide being consumed by the zinc. — Robert Masse, The Conversation, "How do lithium-ion batteries work?," 15 July 2019 Events including the Cuban missile crisis, and even the atom bombs dropped on Japan in World War II, have receded in history. — Robert Weisman, BostonGlobe.com, "Passing the torch: Cardiologist prepares younger colleagues to confront nuclear threat," 12 July 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'atom.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of atom

15th century, in the meaning defined at sense 3

History and Etymology for atom

Middle English, from Latin atomus, from Greek atomos, from atomos indivisible, from a- + temnein to cut

Keep scrolling for more

Keep scrolling for more

More Definitions for atom

atom

noun
How to pronounce atom (audio)

English Language Learners Definition of atom

: the smallest particle of a substance that can exist by itself or be combined with other atoms to form a molecule
: a very small amount of something

See the full definition for atom in the English Language Learners Dictionary

atom

noun
at·​om | \ ˈa-təm How to pronounce atom (audio) \

Kids Definition of atom

1 : the smallest particle of an element that can exist alone or in combination carbon atoms
2 : a tiny particle : bit “I don't believe there's an atom of meaning in it.”— Lewis Carroll, Alice's Adventures in Wonderland

atom

noun
at·​om | \ ˈat-əm How to pronounce atom (audio) \

Medical Definition of atom

: the smallest particle of an element that can exist either alone or in combination

Other Words from atom

atomic \ ə-​ˈtäm-​ik How to pronounce atomic (audio) \ adjective
atomically \ -​i-​k(ə-​)lē

WORD OF THE DAY

jeopardize

play

See Definitions and Examples

Get Word of the Day daily email!