radical

1. (historical, 19th-century Britain, politics) A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).historical

2. (historical, early 20th-century France) A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.historical

3. (arithmetic) A root (of a number or quantity).

4. (linguistics) In logographic writing systems such as the Chinese writing system, the portion of a character (if any) that provides an indication of its meaning, as opposed to phonetic.Examples: "The boy recognised the Chinese characters, though the calligraphy looked a bit strange, as if drawn by someone who had seen them and copied them out radical by radical without knowing what they meant."

5. (linguistics) In Celtic languages, the basic, underlying form of an initial consonant which can be further mutated under the Celtic initial consonant mutations.

6. (linguistics) In Semitic languages, any one of the set of consonants (typically three) that make up a root.