Radical

**Radical**, from Late Latin _radicalis_ "of roots" and from Latin _radix_ "root", may refer to:

- in science and mathematics
- A radical (chemistry) is an atom, molecule, or ion which is likely to take part in chemical reactions.
- Radical symbol (√), a symbol used to indicate the square root or nth root
- Radical of an algebraic group, a concept in algebraic group theory
- Radical of an ideal, an important concept in abstract algebra
- Radical of a ring, in ring theory, a branch of mathematics, a radical of a ring is an ideal of "bad" elements of the ring
- Radical of a module, in the theory of modules, the radical of a module is a component in the theory of structure and classification
- Jacobson radical, the Jacobson radical of a ring, R, consists of those elements in R which annihilate all simple right R-modules
- Nilradical of a ring, the nilradical of a commutative ring is a nilpotent ideal, which is as large as possible
- Nilradical of a Lie algebra, the nilradical of a lie algebra is a nilpotent ideal, which is as large as possible
- Radical of an integer, a concept in number theory
- Symmetric bilinear form, a concept in linear algebra
- Radical of a Lie algebra, a concept in lie theory

- in medicine
- Radical surgery, surgery carried out in extreme circumstances and/or with extensive treatment

- in linguistics
- Root (linguistics), also called a "radical", the form of a word after any prefix<nowiki/>es and suffix<nowiki/>es are removed
- Radical (Chinese character), part of a Chinese character under which it is indexed in a dictionary (also called bùshǒu 部首)
- Radical, one of the three consonants in a Semitic root
- Radical consonant, a consonant articulated with the root of the tongue

- in politics
- Political radicalism
    - Radicalism (historical), the Radical Movement which began in late 18th century Britain and spread to continental Europe and Latin America in the 19th century
    - Radical left, another term for the far left
    - Radical right, another term for the far right
    - radical - a person who shows a strong political stand point
Extremism, political standpoints that are perceived as revolutionary or extreme
- Radical Whigs, influential early writers on Radicalism
- Radical Reformation, an Anabaptist movement at the time of the Protestant Reformation
- Radical Republicans, a member of an influential group of American politicians during the Civil War reconstruction
- Radical Party, one of a number of political parties around the world
- Radicals (UK), parliamentary progressives who were part of the nineteenth-century Liberal coalition
- Radical feminism, a current within feminism that focuses on patriarchy as a system of power
- Radical veganism, a radical interpretation of veganism, usually combined with anarchism

- in culture
- Radical chic, a term coined by Tom Wolfe to describe the pretentious adoption of radical causes by celebrities, socialites, and high society

- in architecture
- Radical Baroque, an architectural style characterized by the curvature of walls and intersection of oval spaces

- brands, titles and proper names
- Radical Sportscars, an English sports car maker
- Radical Entertainment, a video game developer based in Vancouver, Canada
- Free Radical Design, a video game developer based in Nottingham, England
- Free Radicals (band), a jazz-funk musical group from Houston, Texas
- Free Radical Centre, a centre for free radical chemistry and biotechnology that was established in 2005
- _Radical_ (Smack album), Smack's fourth studio album, released in 1988