Definitions from Wiktionary, a free dictionary

[ English

[ Etymology

Latin radicalis.

[ Pronunciation

• enPR: rădʹĭk-əl, IPA: /ˈɹædɪkəl/, SAMPA: /"r{dIk@l/

[ Homophones

• radicle

[ Adjective

radical (comparative more radical, superlative most radical)

1. (botany, not comparable) Of or pertaining to a root (of a plant).
2. Of or pertaining to the intrinsic nature of something.
3. Thoroughgoing.

   The spread of the cancer required radical surgery, and the entire organ was removed.

4. Favouring fundamental change, or change at the root cause of a matter.

   His beliefs are radical.

5. (linguistics, not comparable) Of or pertaining to the root of a word.
6. (chemistry, not comparable) Involving free radicals
7. (slang) Excellent.

   That was a radical jump!

[ Derived terms

• radical empiricism
• radical feminism
• radical left
• radically
• radical pluralism
• radical reform
• radical right
• radical vinegar

[ Translations

[ Noun

radical (plural radicals)

Wikipedia has an article on:

Radical

Wikipedia

1. (historical: 19th-century England) A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).
2. (historical: early 20th-century France) A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.
3. A person with radical opinions.
4. (arithmetic) A root (of a number or quantity).
5. (linguistics) In logographic writing systems as the Chinese writing system, the portion of a character (if any) that provides an indication of its meaning, as opposed to phonetic.
6. (linguistics) In Semitic languages, any one of the set of consonants (typically three) that make up a root.
7. (chemistry) A group of atoms, joined by covalent bonds, that take part in reactions as a single unit.
8. (organic chemistry) A free radical.

[ Derived terms

• free radical
• radical sign

[ Translations

[ French

[ Pronunciation

•  audio^{help, file}
• IPA: /ʁa.di.kal/
• SAMPA: /Ra.di.kal/

[ Adjective and noun