atom

US /ˈæt̬.əm/

UK /ˈæt̬.əm/

1.

the basic unit of a chemical element, consisting of a nucleus and orbiting electrons

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Water is made up of hydrogen and oxygen atoms.

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The smallest particle of an element is an atom.

2.

a tiny particle or amount of something

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There isn't an atom of truth in what he said.

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She didn't show an atom of fear.

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particle speck iota bit trace

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atomic atomic energy