from The American Heritage® Dictionary of the English Language, 4th Edition

  • adj. Arising from or going to a root or source; basic: proposed a radical solution to the problem.
  • adj. Departing markedly from the usual or customary; extreme: radical opinions on education.
  • adj. Favoring or effecting fundamental or revolutionary changes in current practices, conditions, or institutions: radical political views.
  • adj. Linguistics Of or being a root: a radical form.
  • adj. Botany Arising from the root or its crown: radical leaves.
  • adj. Slang Excellent; wonderful.
  • n. One who advocates fundamental or revolutionary changes in current practices, conditions, or institutions: radicals seeking to overthrow the social order.
  • n. Mathematics The root of a quantity as indicated by the radical sign.
  • n. An atom or a group of atoms with at least one unpaired electron.
  • n. Linguistics See root1.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • adj. Favouring fundamental change, or change at the root cause of a matter.
  • adj. Of or pertaining to a root (of a plant).
  • adj. Of or pertaining to the intrinsic nature of something.
  • adj. Thoroughgoing.
  • adj. Of or pertaining to the root of a word.
  • adj. Involving free radicals
  • adj. Excellent.
  • n. A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).
  • n. A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.
  • n. A person with radical opinions.
  • n. A root (of a number or quantity).
  • n. 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.
  • n. In Semitic languages, any one of the set of consonants (typically three) that make up a root.
  • n. A group of atoms, joined by covalent bonds, that take part in reactions as a single unit.
  • n. A free radical.

from the GNU version of the Collaborative International Dictionary of English

  • adj. Of or pertaining to the root; proceeding directly from the root.
  • adj. Hence: Of or pertaining to the root or origin; reaching to the center, to the foundation, to the ultimate sources, to the principles, or the like; original; fundamental; thorough-going; unsparing; extreme
  • adj.
  • adj. Belonging to, or proceeding from, the root of a plant.
  • adj. Proceeding from a rootlike stem, or one which does not rise above the ground.
  • adj. Relating, or belonging, to the root, or ultimate source of derivation.
  • adj. Of or pertaining to a radix or root
  • n.
  • n. A primitive word; a radix, root, or simple, underived, uncompounded word; an etymon.
  • n. A primitive letter; a letter that belongs to the radix.
  • n. One who advocates radical changes in government or social institutions, especially such changes as are intended to level class inequalities; -- opposed to conservative.
  • n.
  • n. A characteristic, essential, and fundamental constituent of any compound; hence, sometimes, an atom.
  • n. Specifically, a group of two or more atoms, not completely saturated, which are so linked that their union implies certain properties, and are conveniently regarded as playing the part of a single atom; a residue; -- called also a compound radical. Cf. Residue.
  • n. A radical quantity. See under Radical, a.
  • n. A radical vessel. See under Radical, a.

from The Century Dictionary and Cyclopedia

  • Pertaining or relating to a root or to roots.
  • Specifically— In botany, belonging to the root: opposed to cauline. See radical leaves and radical peduncle, below.
  • In philology, of the nature of or pertaining to a root, or a primary or underived word or main part of a word: as, a radical word; a radical letter or syllable; radical accentuation.
  • In mathematics, consisting of or indicating one of the roots of a number: as, a radical expression; the radical sign.
  • In chem., noting any atom or group of atoms which is, for the moment, regarded as a chief constituent of the molecules of a given compound, and which does not lose its integrity in the ordinary chemical reactions to which the substance is liable.
  • Making part of the essential nature of the subject or thing concerned; existing inherently; intrinsic; organic: as, radical defects of character; a radical fault of construction; the radical principles of an art or of religion.
  • Of or pertaining to the root or foundation of the subject; concerned with or based upon fundamental principles; hence, thoroughgoing; extreme: as, a radical truth; a radical difference of opinion; radical views or measures; the Radical party in British politics.
  • Of or pertaining to a political party or body of persons known as Radicals (see II., 4, below): as, a Radical candidate; the Radical program.
  • Synonyms There may be a distinction between a radical reform, change, cure, or the like, and one that is thorough, entire, complete, or thoroughgoing, radical emphasizing only the fact of going to the root, whether there is thoroughness or entireness or not. Yet that which is radical is likely to be thorough, etc.
  • n. In philology:
  • n. A radical word or part of a word; especially, a primitive word or verbal element serving as a root of inflected or derivative words.
  • n. A radical letter; a letter forming an essential part of the primitive form or root of a word. Also radicle.
  • n. In chem., an element or group of combined elements which remains after one or more elements have been removed from a compound. (See the quotation.)
  • n. In music, same as root.
  • n. A person who holds or acts according to radical principles; one who pursues a theory to its furthest apparent limit; an extremist, especially in politics.
  • n. In algebra, a quantity expressed as a root of another quantity.
  • n. See the adjectives.
  • In astrology, belonging to the radix or original scheme of nativity; in horary astrology, ripe and proper for judgment.
  • n. A minute vessel which unites with others to form a large branch or trunk. See radicle, 2.
  • n. In England, the name given to a white hat which was formerly somewhat worn by Radicals, owing to the fact that Henry Hunt [a radical English politician, 1773–1835] wore a white hat at various political gatherings in 1820.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. (chemistry) two or more atoms bound together as a single unit and forming part of a molecule
  • n. (linguistics) the form of a word after all affixes are removed
  • adj. especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem
  • n. (mathematics) a quantity expressed as the root of another quantity
  • adj. of or relating to or constituting a linguistic root
  • adj. arising from or going to the root or source
  • n. a character conveying the lexical meaning of a logogram
  • adj. (used of opinions and actions) far beyond the norm
  • n. a person who has radical ideas or opinions
  • adj. markedly new or introducing radical change
  • n. an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule that has lost an electron and will stabilize itself by stealing an electron from a nearby molecule


from The American Heritage® Dictionary of the English Language, 4th Edition

Middle English, of a root, from Late Latin rādīcālis, having roots, from Latin rādīx, rādīc-, root.

from Wiktionary, Creative Commons Attribution/Share-Alike License

From French radical, from Late Latin radicalis ("of or pertaining to the root, having roots, radical"), from Latin radix ("root"); see radix.


  • Pitch must be considered under three heads: first, as referring to the prevailing elevation of tone assumed by the voice in the reading of a whole sentence, passage, or selection, called _general_ or _sentential pitch_; second, as referring to the degree of elevation assumed by the voice in the utterance of the opening, or radical, of any syllable, called _initial_ or _radical pitch_; third, as referring to the tone-width of the intervals in the utterance of the syllable concrete.

    The Ontario Readers: The High School Reader, 1886

  • The word radical comes from the Latin word radis, which means roots.

    Rediscovering Values

  • Obama administration, categorically refuse to even use the term "radical Islam" in order to excise the term from the American vernacular.

    NY Daily News

  • Even the word radical was a seductive conceptual trap.

    The Emperor of All Maladies

  • Halsted called this procedure the “radical mastectomy,” using the word radical in the original Latin sense to mean “root”; he was uprooting cancer from its very source.

    The Emperor of All Maladies

  • It is not clear to me whether Sheik Musa Admani actually used the term radical himself, but the sentence about senior police officers is certainly the wording of the BBC writer.

    Biased BBC

  • One thing people need to understand about the term radical is that it is every bit as mythologized as the cholesterol-heart disease “link.”

    The Vegetarian Myth | The Blog of Michael R. Eades, M.D.

  • Generally, the term radical is not applied to Americanism, just Marxism, which suggests that it is the economics if anything, their chief difference, that is being referred to with the label radical as applied to Marxism.

    On Liberalism, American Conservatism and Reactionary neo-Conservatism: exploiting ambiguous nomenclature

  • As Chris Sciabarra never tires of teaching us, the term radical derives from radix, root; a radical was originally someone whose analysis or action supposedly went to the root of social phenomena, and someone who was radicalized was someone whose focus and action were driven from the superficial elements of the situation to its roots.

    Semantic quibbles #3: Conservatism

  • PILGRIM: And this month, in another language shift, President Bush began using the term radical Islam or Islamic radicals, and today repeatedly and emphatically used both terms in a speech in Norfolk, Virginia.

    CNN Transcript Oct 28, 2005


Log in or sign up to get involved in the conversation. It's quick and easy.

  • "In 1637 Descartes was the first to unite the German radical sign √ with the vinculum to create the radical symbol in common use today."


    July 27, 2018

  • &radic

    May 17, 2009

  • A contranym: can mean both "fundamental" or "departure from the usual".

    May 15, 2008

  • Far beyond the norm

    Ex: Radical opinion

    November 20, 2007