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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

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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 in the case of a black hole, those parts aren’t atoms. — Quanta Magazine, "Are We All Wrong About Black Holes?," 10 Sep. 2019 But in the case of a black hole, those parts aren’t atoms. — Wired, "Are We All Wrong About Black Holes?," 8 Sep. 2019 Real hot and cold can be thought of as a measurement of motion: the temperature of water, air, motor oil or any other substance is a measure of the average speed of molecules and atoms within the substance. — Anchorage Daily News, "Thermometers are at work everywhere in cold-conscious Alaska," 7 Sep. 2019 Metal atoms will often bond quite nicely to hydrogen. — Chris Lee, Ars Technica, "Hydride predicted to be superconductive at room temperature," 6 Sep. 2019 The promise of carbon lies with a material called graphene, which is only one carbon atom thick. — Jason Daley, Smithsonian, "Milestone Carbon-Nanotube Microchip Sends First Message: ‘Hello World!’," 30 Aug. 2019 Every kernel of information was swiftly fed into new theories and predictions about radioactivity and atoms. — New York Times, "Overlooked No More: Elizabeth Rona, Pioneering Scientist Amid Dangers of War," 28 Aug. 2019 Vantablack is made from carbon nanotubes, which are tiny carbon cylinders with walls as thin as one atom. — Sophie.erickson, The Verge, "How carbon nanotubes built this bizarre ultrablack material," 20 Aug. 2019 Chemical and biological weapons could also wreak havoc without splitting atoms. — The Economist, "Should America rule out first use of nuclear weapons?," 15 Aug. 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.

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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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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-​ˈtĂ€m-​ik How to pronounce atomic (audio) \ adjective
atomically \ -​i-​k(ə-​)lē How to pronounce atomically (audio) \ adverb

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