noun at·om \ˈa-təm\

: 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

Full Definition of ATOM

:  one of the minute indivisible particles of which according to ancient materialism the universe is composed
:  a tiny particle :  bit
:  the smallest particle of an element that can exist either alone or in combination
:  the atom considered as a source of vast potential energy

Examples of ATOM

  1. There is not an atom of truth to what he said.
  2. <give me just one atom of information about the novel's surprise ending>

Origin of ATOM

Middle English, from Latin atomus, from Greek atomos, from atomos indivisible, from a- + temnein to cut
First Known Use: 15th century

Other Physics Terms

amplitude, centrifugal, centripetal, convection, gradient, hysteresis, kinetic, lase, quantum
ATOMS Defined for Kids


noun at·om \ˈa-təm\

Definition of ATOM for Kids

:  the smallest particle of an element that can exist alone or in combination <carbon atoms>
:  a tiny particle :  bit <“I don't believe there's an atom of meaning in it.” — Lewis Carroll, Alice's Adventures in Wonderland>

Word History of ATOM

The English word atom came from a Greek word atomos, meaning not able to be divided. Ancient Greek philosophers believed that matter could only be divided to the very smallest particles, atoms, which could not be further divided. Modern science revived the atom idea, but it was discovered that even atoms could be split, and that doing so produced great amounts of energy.
Medical Dictionary


noun at·om \ˈat-əm\

Medical Definition of ATOM

:  the smallest particle of an element that can exist either alone or in combination
atom·ic \ə-ˈtäm-ik\ adjective
atom·i·cal·ly \-i-k(ə-)lē\ adverb


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