Radical, from Late Latin radicalis "of roots" and from Latin radix "root", may refer to:

In chemistry:

  • A radical (chemistry) is an atom, molecule, or ion, that is likely to take part in chemical reactions

In mathematics:

  • 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 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 that 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, in number theory, the radical of an integer is the product of the primes which divide that integer
  • Left (or right) radical of a bilinear form, the subspace of all vectors left (or right) orthogonal to every vector.
  • 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:

  • In an inflected language such as English or Spanish, the radical verbs (also called 'radical-changing') are exceptions to the standard patterns of word change (e.g., to be is in most Indo European languages).
  • Root (linguistics), also called a "radical", the form of a word after any prefixes and suffixes 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 that 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 Whigs, influential early writers on Radicalism
  • 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
  • Radicalization

In religion:

  • Radical Reformation, an Anabaptist movement concurrent with the Protestant Reformation
  • Radical Christianity
  • Radical Islam
  • Radical: Taking Back Your Faith from the American Dream, 2010 Christian book

In culture:

  • 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
  • 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

In music:

  • Radical (mixtape), a mixtape by the alternative hip hop collective OFWGKTA
  • "Radicals" (song), a song by Tyler, The Creator from his album Goblin
  • Free Radicals (band), a jazz-funk musical group from Houston, Texas
  • New Radicals, an American pop rock band from the 1990s
  • Radical (album), Smack's fourth studio album, released in 1988

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 Radical Centre, a centre for free radical chemistry and biotechnology that was established in 2005

Famous quotes containing the word radical:

    A radical is a man with both feet firmly planted in the air. A conservative is a man with two perfectly good legs, who, however, has never learned to walk forward. A reactionary is a somnambulist walking backwards. A liberal is a man who uses his legs and his hands at the behest ... of his head.
    Franklin D. Roosevelt (1882–1945)

    Universal suffrage is sound in principle. The radical element is right.
    Rutherford Birchard Hayes (1822–1893)

    Radical Chic, after all, is only radical in Style; in its heart it is part of Society and its traditions—Politics, like Rock, Pop, and Camp, has its uses.
    Tom Wolfe (b. 1931)