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radical



  1. (CHEMISTRY) A group of atoms, either in a compound or existing alone in which all the atomic valences are not satisfied by chemical bonding. Thus, removal of a hydrogen atom from methane, CH4, gives the methy; radical CH3. The term is usually taken to mean a free radical, that is, one existing free for a short time in a reaction.

       • PHYSICAL CHEMISTRY


  2. (MATHEMATICS) The root of a number or quantity. The radical sign is √, or more generally n√. It seems to have been first used in 1525 by Christoff Rudolff (1499–1545) in his Die Coss. Another way of expressing the nth of a number x1/n.

       • SYMBOLS AND NOTATION