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atom (EN)
noun

noun “atom”

singular atom, plural atoms
  1. the tiniest piece of a chemical element, made up of a nucleus surrounded by tiny particles called electrons
    An atom of hydrogen is made up of one proton and one electron.
  2. (in ancient Greek philosophy) the smallest particle of matter that could not be divided into smaller parts
    Ancient Greek philosophers believed that everything was made up of tiny, indivisible atoms.