Definition of radical in English:

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Pronunciation: /ˈradək(ə)l/


1(Especially of change or action) relating to or affecting the fundamental nature of something; far-reaching or thorough: a radical overhaul of the existing regulatory framework
More example sentences
  • Both groups would be affected by a radical change in the business climate.
  • Are the arguments of those who predict a radical change in the nature of 21st century wars that groundless after all?
  • The people are exhausted from the radical changes that affect their way of life.
thoroughgoing, thorough, complete, total, comprehensive, exhaustive, sweeping, far-reaching, wide-ranging, extensive, across the board, profound, major, stringent, rigorous
1.1Forming an inherent or fundamental part of the nature of someone or something: the assumption of radical differences between the mental attributes of literate and nonliterate peoples
More example sentences
  • He said yesterday: ‘Football results do not make a radical difference to society but they can have an impact.’
  • Note also the radical difference between how our culture defines ‘fashionable’ thinness for men and women.
  • As for the property rights of authors to their works, the consequences of these differences are radical.
fundamental, basic, essential, quintessential;
structural, deep-seated, intrinsic, organic, constitutive
1.2(Of surgery or medical treatment) thorough and intended to be completely curative.
Example sentences
  • The principal concern is that age bias will lead to the use of palliative therapies as opposed to curative treatments and radical surgical procedures in older adult patients.
  • More serious cancers, however, will require radical surgery, radiotherapy, and chemotherapy.
  • In patients who are unfit to have radical surgery, radiotherapy may be administered to the inguinal lymph nodes.
1.3Characterized by departure from tradition; innovative or progressive: a radical approach to electoral reform
More example sentences
  • Given the extent to which it is taken for granted today, it can be difficult to fully appreciate the truly innovative and radical approach Frege took to logic.
  • The resulting album attracted two nominations in the Radio 2 folk awards with its radical approach to traditional music.
  • She calls for a radical re-examination of traditional approaches to accountability, transparency and press freedom.
2Advocating or based on thorough or complete political or social change; representing or supporting an extreme or progressive section of a political party: a radical American activist
More example sentences
  • Wales has always had strong left wing and radical political parties and leaders.
  • She has been the most radical advocate of the party's adoption of an independent stance in elections.
  • Hard-liners formed a radical political party, more extremist than any other.
revolutionary, progressive, reformist, revisionist, progressivist;
extreme, extremist, fanatical, militant, diehard, hard-core
3Relating to the root of something, in particular.
3.1 Mathematics Of the root of a number or quantity.
Example sentences
  • The answers are thirteen over four and two plus or minus radical seven.
3.2Denoting or relating to the roots of a word.
3.3 Music Belonging to the root of a chord.
3.4 Botany Of, or springing direct from, the root or stem base of a plant.
4 [usually as exclamation] North American informal Very good; excellent: Okay, then. Seven o’clock. Radical!


1A person who advocates thorough or complete political or social reform; a member of a political party or part of a party pursuing such aims.
Example sentences
  • The party has not tried to disguise its new deregulatory approach, which is causing unease among party radicals and old-style social democrats.
  • I try to be a radical in political and social ways, but I'm a terrible conservative when it comes to technology.
  • Rohm was not really a social or political radical.
revolutionary, progressive, reformer, revisionist;
informal ultra
2 Chemistry A group of atoms behaving as a unit in a number of compounds. See also free radical.
Example sentences
  • Examples of compounds or groups that accept anions include the nitrate and hydroxide radicals.
  • Marcel Nicolet resolved some of this discrepancy by showing how reactive molecular fragments called radicals convert ozone molecules back into O 2.
  • Subsequent oxidation-reduction reactions can also produce superoxide anions, hydrogen peroxide and hydroxyl radicals.
3The root or base form of a word.
Example sentences
  • The word can refer to a geminate verb, i.e., a triliteral verb where the second and third radicals are the same - also called mediae geminatae.
3.1Any of the basic set of 214 Chinese characters constituting semantically or functionally significant elements in the composition of other characters and used as a means of classifying characters in dictionaries.
Example sentences
  • By learning the function of radicals of Chinese characters, students can learn new characters by groups and strings.
  • Finally, the Lexical Decision test is a measure of children's right-left spatial reversals of Chinese radicals.
  • There are about 200 radicals representing basic subjects.
4 Mathematics A quantity forming or expressed as the root of another.
Example sentences
  • In 1845 Wantzel, continuing his researches into equations, gave a new proof of the impossibility of solving all algebraic equations by radicals.
  • From its true emergence, algebra can be seen as a theory of equations solved by means of radicals, and of algebraic calculations on related expressions.
  • When the exponent is a prime number, I say that its radical cannot be divisible by any other prime except those that are greater by one than a multiple of double the exponent.
4.1A radical sign.



Example sentences
  • He had become a Tendai Buddhist at this temple - imagine the radicalness of that in Victorian times!
  • The problem wasn't with their radicalness but their absurd level of self-importance.
  • It also stems from the thoroughness with which he examined Western philosophical traditions, especially from Kant onward, and the radicalness to his critique of contemporary Western society.


Late Middle English (in the senses 'forming the root' and 'inherent'): from late Latin radicalis, from Latin radix, radic- 'root'.

  • The earliest sense of radical is ‘having to do with the basic nature of something, fundamental’, and it goes back to Latin radix ‘root’, the source also of eradicate (Late Middle English) ‘to root out’ and radish (Old English), and related to root. In political terms, a radical is someone who wants complete political or social reform—to be achieved by going to the root of the problem. In the 1970s, the American writer Tom Wolfe coined radical chic for a fashionable affectation of radical left-wing views.

For editors and proofreaders

Syllabification: rad·i·cal

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