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

The seismometers, which are designed to measure surface movements less than the width of a hydrogen atom, will produce what are essentially sonograms of the planet’s insides. Paul Roberts, The Seattle Times, "Mars landing is a nail-biter for Redmond rocket engineers," 26 Nov. 2018 Basically, hydrogen atoms from neighboring polymers are weakly attracted to each other. Chris Lee, Ars Technica, "Big transistor senses the arrival of a single molecule," 29 Oct. 2018 If a hydrogen atom were the size of Earth, the proton at its center would fit inside the Ohio State football stadium. Author: Sarah Kaplan, Anchorage Daily News, "In a cosmic first, scientists detect ‘ghost particles’ from a distant galaxy," 12 July 2018 If a hydrogen atom were the size of Earth, the proton at its center would fit inside the Ohio State football stadium. Sarah Kaplan, chicagotribune.com, "In a cosmic first, scientists detect 'ghost particles' from a distant galaxy," 12 July 2018 Made hot enough for long enough, hydrogen atoms can fuse together to form helium, like in the center of stars, releasing in the process a tremendous amount of energy. Dino Grandoni, Washington Post, "The Energy 202: Trump administration must decide whether to back the biggest nuclear fusion project ever," 7 Mar. 2018 The silicon absorbs the infrared photons, generating two electrons for every photon of blue light that hit a ytterbium atom. Chris Lee, Ars Technica, "Transparent solar cell turns edge on and generates its own light," 12 Dec. 2018 Single crystal graphene, a material only one atom thick but many times stronger than steel, is another possibility. Colin Stuart, WSJ, "Will Elevators to Outer Space Ever Get Off the Ground?," 20 Sep. 2018 The government agency created atoms known as Bose-Einstein condensates (BECs) for the first time in orbit to focus on their unusual quantum behavior. Chris Ciaccia, Fox News, "NASA has created the coldest spot ever," 9 Aug. 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

16 Feb 2019

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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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