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Medical Dictionary

noun \ˈī-ən, ˈī-ˌän\

Medical Definition of ion

  1. 1:  an atom or group of atoms that carries a positive or negative electric charge as a result of having lost or gained one or more electrons—see anion, cation

  2. 2:  a charged subatomic particle (as a free electron)





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a division or portion of a pool or whole

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