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Pronunciation: rad'i-kal


  1. In chemistry, a group of elements or atoms usually passing intact from one compound to another, but usually incapable of prolonged existence in a free state (methyl, CH3); in chemical formulas, a radical is often distinguished by being enclosed in parentheses or brackets.
  2. Thorough or extensive; relating or directed to the extirpation of the root or cause of a morbid process; a radical operation.
  3. Denoting treatment by extreme, drastic, or innovative, as opposed to conservative, measures.
  4. A functional group in a molecule or molecular entity.

Synonym(s): free radical

[L. radix (radic-), root]

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© Copyright 2018 Wolters Kluwer. All Rights Reserved. Review date: Sep 19, 2016.