Definition of atom in English:



  • 1The smallest particle of a chemical element that can exist.

    Atoms consist of a tiny, dense, positively charged nucleus made of neutrons and protons, surrounded by a cloud of negatively charged electrons, roughly 10⁻⁸ cm in diameter. Each chemical element consists of atoms with a characteristic number of protons. Atoms are held together in molecules by the sharing of electrons

    • ‘If it were a little more curved it would collapse, imploding on itself in a cosmic crunch; a little less curved, and every star, planet, sun and galaxy would fly apart from each other and so would every atom of matter in each of them.’
    • ‘It reminds me of cell division in an embryo or the arrangement of atoms in a molecule.’
    • ‘Everything is physical; the only things that exist consist of atoms in motion.’
    • ‘This is caused by the movement of an atom or group of atoms from one position to another.’
    • ‘Until now it has been impossible for scientists to detect every atom in the structure of protein molecules, which play a vital role in the body.’
    • ‘Recall also that one of the initial triumphs of quantum mechanics was to explain the stability of atoms.’
    • ‘Ordinary gas is made from atoms that consist of electrons orbiting around nuclei.’
    • ‘Polychlorinated dibenzodioxin is 10 times more potent a toxin than hexachlorodibenzodioxin, even though the difference is just one chlorine atom.’
    • ‘As can be seen, each silicon atom bonds together with four of its neighbors to form a rigid crystal structure.’
    • ‘In simulations it is possible to calculate atom density, mass density, and electron density profiles.’
    • ‘Water seems like the perfect energy source, packed, as it is, with two atoms of hydrogen per molecule.’
    • ‘Radioactive atoms decay into stable atoms by a simple mathematical process.’
    • ‘Once removed from an atom, an electron may in turn ionize other atoms or molecules.’
    • ‘Until now, molecules with fewer than 60 carbon atoms have only been made in the gaseous phase.’
    • ‘Bacteria that can break down chlorinated compounds have been known for years, but none that could remove the last chlorine atom to complete the detoxification.’
    • ‘The world of atoms and photons does not follow the rules of classical physics.’
    • ‘Lam says that teleporting single atoms and molecules could be perfected within the next ten years.’
    • ‘By the end of the century J. I. Thomson would reveal that atoms could also be divided into parts.’
    • ‘Dr Lewis said the acrosome reaction involved the channelling of charged calcium atoms, or ions.’
    • ‘Since all the variety we see around us is just a product of different arrangements of a few types of atom, nanotech has been hyped as a potentially limitless miracle technology.’
    • ‘They have six atoms of carbon in each molecule and are therefore called hexoses.’
    • ‘As early as 1991 Japanese researchers discovered that carbon atoms can form tiny tubes whose walls are just one atom thick.’
    • ‘Its atoms have a nucleus of two protons and two neutrons, orbited by two electrons.’
    • ‘These are electrically charged atoms of magnesium that form part of the gas surrounding a black hole.’
    • ‘Each radium atom is decaying into four more alpha-emitting radionuclides, creating in all 12,500 particles.’
    • ‘At the time, it was believed that electrons colliding with atoms always lost energy.’
    • ‘The electric field set up inside the tube excites atoms of mercury gas, making them emit ultraviolet light.’
    particle, molecule, bit, little bit, tiny bit, tiny piece, fragment, fraction, grain, granule, crumb, morsel, mite, mote, speck, spot, dot
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    1. 1.1usually the atom Atomic particles as a source of nuclear energy.
      ‘the power of the atom’
      • ‘After all, they had lived at the end of fifty years of fantastic technological advancement, with powered flight becoming common, the power of the atom having been harnessed and computers having been created.’
      • ‘Written as a memoir, the book provides his unparalleled insight into the use and abuse of the power of the atom.’
      • ‘In 1900 nobody could have anticipated 80% of France's electrical power would come from a source not known at that time: the atom.’
      • ‘One day soon, man is going to be able to harness incredible energies, maybe even the atom, energies that could ultimately hurl us to other worlds in some sort of spaceship.’
      • ‘The towering mushroom cloud is usually regarded as a symbol of the Nuclear Age, but in fact this phenomenon was first witnessed eighty-five years ago, before the power of the atom was recognised or released.’
      • ‘When the atom's potential was realized, physicists and nuclear engineers became a kind of protected species.’
      • ‘It all started with the discovery of the atom, and how splitting it could release vast amounts of energy.’
      • ‘Over the centuries, people have turned to steam, to coal, to oil, even to the atom for their energy.’
      • ‘Will they turn the awesome power of the atom upon themselves as we have done?’
      • ‘‘Today we're just going to learn about atom splitting,’ she started off.’
      • ‘Heisenberg is already very famous as a scientist, and when the war starts, he will work for the Nazis trying to split the atom and develop an atomic bomb.’
      • ‘Rutherford knew that alpha particles, which readily pierced the atom's cloud of electrons, didn't have enough energy to penetrate and pry apart the nucleus.’
      • ‘They showed us how to split the atom and harness nuclear fuel so that we might finally meet them as equals.’
      • ‘America rose up and rebelled, and then expanded in power until it tipped the balance during World War One and harnessed the power of the atom to win World War Two.’
      • ‘Bohr and Heisenberg are among the first to realize that in splitting the atom mankind has acquired the power to destroy itself.’
      • ‘It's 60 years ago tomorrow since the world became aware of the awesome destructive power of the atom.’
    2. 1.2usually with negative An extremely small amount of something.
      ‘I shall not have one atom of strength left’
      • ‘Instead I just stood and stared at the sign and remembered their halcyon days when I loved them with every atom of my being.’
      • ‘You wonder how she doesn't deflate like a ruptured balloon at the end of every song; she seems to throw every atom inside her into each note.’
      • ‘It is the height of hypocrisy for him to complain that Darwinism lacks causal specificity when his own theory lacks any specificity, including one atom of historical concreteness.’
      • ‘Staring at the endless universe, looking at the twinkling stars and pondering the infinitesimally tiny atom of matter or the gene that makes us up, helps to put issues of religion in true perspective.’
      • ‘Was this, as I suspected in every atom of my being, a cooked sausage that just wasn't properly cooked?’
      • ‘He was their property, heart and soul, body and blood; what they did claimed every atom of him, sleeping and waking; it colored life and dictated the terms of death.’
      • ‘It is still a spillage and by the terms of the sign even the spillage of one atom's worth of petrol should be reported.’
      • ‘Burning determination gripped every atom of his being.’
      • ‘Leibniz, meanwhile, believed every atom in the universe to have a soul, the universe being a projection through them of God's will, like a cosmic hologram.’
      • ‘Every particle, every atom of me is alive in some way I cannot explain.’
      • ‘Immaculata, 19 years old and high-strung, appears at my bedroom door, hands on hips and nostrils flaring, every atom of her quivering with melodrama.’
      • ‘Every atom of me still wants to hold on to those childish beliefs that sometime in the future it will all be different.’
      • ‘But they know me, every atom of my body, every hair on my head, and they pull me, each one of them, like a multitude of collapsed stars pulling all surrounding light into them forever.’
      • ‘I feel with every atom of my body that it's untrue and wrong.’
      • ‘I will not fail to bring to your notice that this transaction is hitch free and that you should not entertain any atom of fear as all required arrangements have been made for the transfer.’
      • ‘She says that the Supreme One is present in every atom of this world.’
      particle, molecule, bit, little bit, tiny bit, tiny piece, fragment, fraction, grain, granule, crumb, morsel, mite, mote, speck, spot, dot
      View synonyms
  • 2Canadian usually as modifier A level of amateur sport, typically involving children aged between nine and eleven.

    ‘eight atom hockey teams’
    • ‘After having fielded a bantam team for several years, the Storm is now putting together an atom program open to players aged nine and 10.’
    • ‘His hour-long presentation in the curling lounge at the Omniplex proved helpful to many people attending including Chad Anker, an atom level coach from Calgary.’
    • ‘The local Foothills Elite North 93 team won the major atom title, beating the Red Deer Rustlers 5-2.’


Late 15th century: from Old French atome, via Latin from Greek atomos ‘indivisible’, based on a- ‘not’ + temnein ‘to cut’.