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radical

[ rad-i-kuhl ]

/ ˈræd ɪ kəl /

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See synonyms for radical on Thesaurus.com

adjective

of or going to the root or origin; fundamental: There is a radical difference between the two interpretations of the sacred text, one justifying war and the other requiring nonviolent resistance.

extreme, especially as regards change from accepted or traditional forms: a radical change in the policy of the company.

favoring drastic political, economic, or social reforms: radical ideas;radical and anarchistic ideologues.

favoring, supporting, or representing extreme forms of religious fundamentalism: radical fundamentalists and their rejection of modern science.

forming a basis or foundation: What is the radical reason for his choice?

existing inherently in a thing or person: radical defects of character.

characterized by a marked departure from prevailing methods, practices, or ideas, particularly in the arts; experimental; unorthodox:The composer’s radical approach to sound, using timbre and rhythm rather than pitch, was declared “noise” by an influential critic.

Slang. excellent; wonderful; cool; rad: You got here on an electric skateboard? That's radical!

Mathematics.

pertaining to or forming a root.
denoting or pertaining to the radical sign.
irrational (def. 5b).

Grammar. of or pertaining to the root of a word.

Botany. of or arising from the root or the base of the stem.

noun

a person who holds or follows strong convictions or extreme principles; extremist.

a person who advocates fundamental political, economic, and social reforms by direct and often uncompromising methods.

Mathematics.

a quantity expressed as a root of another quantity.
the set of elements of a ring, some power of which is contained in a given ideal.
radical sign.

Chemistry.

Grammar. root¹ (def. 12).

(in Chinese writing) one of 214 ideographic elements used in combination with phonetics to form thousands of different characters.

OTHER WORDS FOR radical

1 basic, essential; original, innate, ingrained.

2 complete, unqualified, thorough; drastic, excessive, immoderate, violent.

See synonyms for radical on Thesaurus.com

OPPOSITES FOR radical

1, 2 superficial.

See antonyms for radical on Thesaurus.com

VIDEO FOR RADICAL

Do You Remember This Radical 80s Slang?

When you re-hear to this 80's slang you'll feel like you've been transported back in time. Do you remember these totally 80's words?

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QUIZ

ALL IN FAVO(U)R OF THIS BRITISH VS. AMERICAN ENGLISH QUIZ

There's an ocean of difference between the way people speak English in the US vs. the UK. Are your language skills up to the task of telling the difference? Let's find out!

Question 1 of 7

True or false? British English and American English are only different when it comes to slang words.

TAKE THE QUIZ TO FIND OUT

Origin of radical

First recorded in 1350–1400; Middle English, from Late Latin rādīcālis “having roots, forming roots,” equivalent to Latin rādīc- (stem of rādix ) + -ālis; see origin at root¹, -al¹

synonym study for radical

2. Radical, extreme, fanatical denote that which goes beyond moderation or even to excess in opinion, belief, action, etc. Radical emphasizes the idea of going to the root of a matter, and this often seems immoderate in its thoroughness or completeness: radical ideas; radical changes or reforms. Extreme applies to excessively biased ideas, intemperate conduct, or repressive legislation: to use extreme measures. Fanatical is applied to a person who has extravagant views, especially in matters of religion or morality, which render that person incapable of sound judgments; and excessive zeal which leads him or her to take violent action against those who have differing views: fanatical in persecuting others.

historical usage of radical

Radical comes straight from the Late Latin adjective rādicālis “having roots, rooted,” first occurring about a.d. 400 in Contra Faustum (“Against Faustus the Manichaean”) by St. Augustine of Hippo. Rādicālis is a derivative of the noun rādix (inflectional stem rādīc- ) “root (of a plant, tooth, hair), root (of a family, stock, breed), (etymological) root.” The mathematical sense “denoting the radical sign which indicates the root of a number” dates from the late 17th century. Radical in its political sense dates from the late 18th century in England and the first half of the 19th century in the United States.
Latin rādix comes from wrād-, one of the variants of the Proto-Indo-European root wrād, werād, wred- “root, branch.” From this same variant Latin also has rāmus “branch” (the root, so to speak, of English ramify ); Greek has rhádix (stem rhádik- ) from the same variant. Another variant of the root is the possible source of Greek rhiza, source of English rhizome (Greek variants include Aeolic briza, brisda and Mycenaean wriza ). Wrād- regularly becomes wrōt- in proto-Germanic, the ultimate source of the English word root.

OTHER WORDS FROM radical

rad·i·cal·ness, nounmul·ti·rad·i·cal, adjectivenon·rad·i·cal, adjective, nounqua·si-rad·i·cal, adjective

sem·i·rad·i·cal, adjectivesub·rad·i·cal, adjectivesu·per·rad·i·cal, adjectiveul·tra·rad·i·cal, adjective, nounun·rad·i·cal, adjective

Words nearby radical

radiative capture, radiative zone, radiator, radiator grille, radiatus, radical, radical axis, radical chic, radical empiricism, radical expression, radicalism

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use radical in a sentence

Old friends who never seemed to care about politics now seem ready to rain blows on those who disagree with their radical views.
Politics and conspiracy theories are fracturing relationships. Here’s how to grieve those broken bonds.|Jeff Schrum|February 11, 2021|Washington Post
We asked them to lay out the steps for this radical classroom transformation.
4 big ideas on fixing American schools|By Sabrina Imbler|February 6, 2021|Popular-Science
An idea born in a Swiss patent office that evolved into a mature theory in Berlin set forth a radical new picture of the cosmos, rooted in a new, deeper understanding of gravity.
Einstein’s theory of general relativity unveiled a dynamic and bizarre cosmos|Elizabeth Quill|February 3, 2021|Science News
The anxiety and loss of community some Q believers may feel can make them more vulnerable to believing radical ideas.
What Comes Next For QAnon Followers|Kaleigh Rogers|January 29, 2021|FiveThirtyEight

Developing radical new technology is inherently risky, but that doesn’t make breaking this news any easier.
Loon’s bubble bursts—Alphabet shuts down Internet balloon company|Ron Amadeo|January 22, 2021|Ars Technica
But Brooke was out of step with the New Left and its notion of radical chic.
Ed Brooke: The Senate's Civil Rights Pioneer and Prophet of a Post-Racial America|John Avlon|January 4, 2015|DAILY BEAST
Too moderate and the more radical groups call you a snitch, jeopardizing your standing and authority at demonstrations.
De Blasio and the New York City Protesters Have No Blood on Their Hands|Jacob Siegel|December 22, 2014|DAILY BEAST
He has become the most radical pope in modern memory for his economic populism.
How Pope Francis Became the World’s BFF|Jason Berry|December 21, 2014|DAILY BEAST
He branded it a fifth-column invasion into popular culture, normalizing radical, even communist ambitions.
Glenn Beck Is Now Selling Hipster Clothes. Really.|Ana Marie Cox|December 20, 2014|DAILY BEAST
Two hostages are dead and 15 others free after an Islamic radical took them hostage before police killed him.
Jihadi Siege in Sydney Ends in Gunfight|Courtney Subramanian, Lennox Samuels, Chris Allbritton|December 15, 2014|DAILY BEAST
This letter indirectly points out two long-standing radical errors in engineering phraseology.
Life of Richard Trevithick, Volume II (of 2)|Francis Trevithick
Decandolle's observations regarding the radical excretions of plants have not been confirmed by subsequent observers.
Elements of Agricultural Chemistry|Thomas Anderson
But if this reincarnation was quite ordinary in its process, it was the more radical and decisive.
The Life & Letters of Peter Ilich Tchaikovsky|Modeste Tchaikovsky
There are two radical differences between Humanism and Christianity.
God and my Neighbour|Robert Blatchford
If the Collier were a Radical, how coal-black the portraits would come out!
Punch, or the London Charivari, Vol. 109, July 27, 1895|Various

British Dictionary definitions for radical

radical

/ (ˈrædɪkəl) /

adjective

of, relating to, or characteristic of the basic or inherent constitution of a person or thing; fundamentala radical fault

concerned with or tending to concentrate on fundamental aspects of a matter; searching or thoroughgoingradical thought; a radical re-examination

favouring or tending to produce extreme or fundamental changes in political, economic, or social conditions, institutions, habits of mind, etca radical party

med (of treatment) aimed at removing the source of a diseaseradical surgery

slang, mainly US very good; excellent

of, relating to, or arising from the root or the base of the stem of a plantradical leaves

maths of, relating to, or containing roots of numbers or quantities

linguistics of or relating to the root of a word

noun

a person who favours extreme or fundamental change in existing institutions or in political, social, or economic conditions

maths a root of a number or quantity, such as ³√5, √ x

Also: radicle chem

short for free radical
another name for group (def. 10)

linguistics another word for root 1 (def. 9)

(in logographic writing systems such as that used for Chinese) a part of a character conveying lexical meaning

Derived forms of radical

radicalness, noun

Word Origin for radical

C14: from Late Latin rādīcālis having roots, from Latin rādix a root

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for radical

radical

[ răd′ĭ-kəl ]

A root, such as √2, especially as indicated by a radical sign (√).

A group of atoms that behaves as a unit in chemical reactions and is often not stable except as part of a molecule. The hydroxyl, ethyl, and phenyl radicals are examples. Radicals are unchanged by chemical reactions.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for radical (1 of 2)

radical

In politics, someone who demands substantial or extreme changes in the existing system.

Cultural definitions for radical (2 of 2)

radical

In chemistry, an atom or group of atoms that has at least one electron free to participate in forming a chemical bond.

notes for radical

In general, radicals are associated with chemical reactions that proceed rapidly.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.