atom

noun
at·​om | \ˈa-təm \

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

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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

But every once in a while, a neutrino will hit into an atom of that ice, and breaks it apart, there’s a momentary flash of an eerie blue light. Brian Resnick, Vox, "Physicists are unveiling cool, new findings from a South Pole neutrino observatory Thursday. Here’s how to watch.," 12 July 2018 Additionally, the time-keeping device on each satellite gives a subtly different reading, the result of variations in their atomic clocks, which tell time by measuring the precise oscillations of an atom. Garrett M. Graff, WIRED, "The New Arms Race Threatening to Explode in Space," 26 June 2018 The two researchers behind the paper, Julian Muñoz and Avi Loeb, propose that instead of an individual particle, dark matter forms a composite particle akin to an atom. John Timmer, Ars Technica, "Could dark matter atoms explain a recent observation?," 3 June 2018 When a public event staged by members of the British royal family is executed correctly, the overall picture inspires white-hot jealousy powerful enough to split an atom. Caity Weaver, New York Times, "I Also Went to the Royal Wedding," 24 May 2018 GenX compounds are short-chain PFAS molecules, with only six carbon atoms, and some research indicated that a shorter chain might be less toxic and less likely to build up in organisms. Ken Otterbourg, Fortune, "Teflon’s River of Fear," 24 May 2018 The Kilopower project uses nuclear fission — the process in which an atom is split, releasing a tremendous amount of heat energy. Rob Nikolewski, sandiegouniontribune.com, "NASA looks to send a small nuclear reactor to the moon and Mars," 23 May 2018 Rice University chemist James Tour, the study's senior author, says the laser's intense light and heat rearrange carbon atoms and form bonds among them. Prachi Patel, Scientific American, "The Quirkier Uses of Graphene," 16 May 2018 The light arose from the collision between a remarkably energetic neutrino – a wraithlike subatomic particle moving close to the speed of light – and the nucleus of a hydrogen or oxygen atom deep within the ice. Eoin O'carroll, The Christian Science Monitor, "Neutrino demonstration heralds a new way of observing the cosmos," 12 July 2018

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.

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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

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Dictionary Entries near atom

atoke

atole

atoll

atom

atomate

atom beam

atomic

Statistics for atom

Last Updated

26 Oct 2018

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Time Traveler for atom

The first known use of atom was in the 15th century

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More Definitions for atom

atom

noun

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

atom

noun
at·​om | \ˈa-təm \

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 \

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 \ adjective
atomically \ -​i-​k(ə-​)lē \ adverb

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More from Merriam-Webster on atom

Thesaurus: All synonyms and antonyms for atom

Spanish Central: Translation of atom

Nglish: Translation of atom for Spanish Speakers

Britannica English: Translation of atom for Arabic Speakers

Britannica.com: Encyclopedia article about atom

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