What is a radical in organic chemistry?

A radical is a molecule that contains at least one unpaired electron. Most molecules contain an even number of electrons, and the covalent chemical bonds that hold atoms together within a molecule are usually made up of pairs of electrons shared together by bonded atoms. Most radicals can be thought to arise from the cleavage of normal electron paired bonds, with each cleavage creating two separate entities, each containing one unpaired electron (in addition to the normal, paired number of electrons of the atoms).