rad·i·cal

noun /ˈradikəl/  radicals, plural A person who advocates thorough or complete political or social reform; a member of a political party or part of a party pursuing such aims A group of atoms behaving as a unit in a number of compounds The root or base form of a word Any of the basic set of 214 Chinese characters constituting semantically or functionally significant elements in the composition of other characters and used as a means of classifying characters in dictionaries A quantity forming or expressed as the root of another A radical sign