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

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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

Most of the uranium atoms found in nature are U-238, an isotope with 92 protons and 146 neutrons. Stephanie Demarco, latimes.com, "210,000-year-old skull in Greece is earliest sign of modern humans in Europe or Asia," 10 July 2019 During a PET scan, a patient is injected with biologically active molecules known as tracers, which are tagged with radioactive atoms. Julie Grisham, Scientific American, "Faster, clearer PET images offer new views on disease," 9 July 2019 Spectroscopy defines how light interacts with atoms in a star’s upper layers. David Grossman, Popular Mechanics, "How the Galaxy's Stars Build a 'Netflix for Exoplanets'," 25 June 2019 Enrichment basically means stripping away atoms of another isotope, called U-238. Jon Gambrell, BostonGlobe.com, "Iran says it will break uranium stockpile limit in 10 days," 17 June 2019 Enrichment basically means stripping away atoms of another isotope, called U-238. Jon Gambrell, Fortune, "Iran Says It Will Break Uranium Stockpile Limit in 10 Days," 17 June 2019 One atom of chlorine can destroy more than 100,000 ozone molecules, according to the U.S. Environmental Protection Agency, eradicating ozone much more quickly than it can be replaced. Mark Thiessen, National Geographic, "Ozone depletion, explained," 18 Apr. 2019 Hayabusa2 is powered by ion engines, which accelerate charged atoms of xenon with an electric field to generate thrust. Kenneth Chang, New York Times, "Japan’s Hayabusa2 Spacecraft Creeps Up on the Ryugu Asteroid," 25 June 2018 The question is how to interpret the bizarre analogy between a fluid of rubidium atoms in a lab in Israel and the mysterious astrophysical abysses most often created when huge stars exhaust their fuel and collapse inward. Quanta Magazine, "Philosophers Debate New ‘Sonic Black Hole’ Discovery," 30 June 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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Dictionary Entries near atom

atoke

atole

atoll

atom

atomate

atom beam

atomic

Statistics for atom

Last Updated

20 Jul 2019

Look-up Popularity

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 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 How to pronounce atomically (audio) \ 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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