Origin of radical

1350–1400; Middle English < Late Latin rādīcālis “having roots,” equivalent to Latin rādīc- (stem of rādīx) root1 + -ālis -al1
Related formsrad·i·cal·ness, nounmul·ti·rad·i·cal, adjectivenon·rad·i·cal, adjective, nounqua·si-rad·i·cal, adjectivesem·i·rad·i·cal, adjectivesub·rad·i·cal, adjectivesu·per·rad·i·cal, adjectiveul·tra·rad·i·cal, adjective, nounun·rad·i·cal, adjective

Synonyms for radical

Synonym study

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.

Antonyms for radical

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for radical

Contemporary Examples of radical

Historical Examples of radical

  • The difference too is radical; it goes to the heart of the mystery.

    'Tis Sixty Years Since

    Charles Francis Adams

  • The influence of Westhampton is Radical, and fills the Council with a lot of outsiders.


    William J. Locke

  • "Yes, by that Radical miller who lives at Martover," said Marion.

    The Coryston Family

    Mrs. Humphry Ward

  • For under all her radical talk Sue had the kindest heart in the world.

    The Harbor

    Ernest Poole

  • Into my reverie that night Sue burst with a dozen radical friends.

    The Harbor

    Ernest Poole

British Dictionary definitions for radical



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


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
  1. short for free radical
  2. 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 Formsradicalness, 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

Word Origin and History for radical

late 14c., in a medieval philosophical sense, from Late Latin radicalis "of or having roots," from Latin radix (genitive radicis) "root" (see radish). Meaning "going to the origin, essential" is from 1650s. Radical sign in mathematics is from 1680s.

Political sense of "reformist" (via notion of "change from the roots") is first recorded 1802 (n.), 1817 (adj.), of the extreme section of the British Liberal party (radical reform had been a current phrase since 1786); meaning "unconventional" is from 1921. U.S. youth slang use is from 1983, from 1970s surfer slang meaning "at the limits of control." Radical chic is attested from 1970; popularized, if not coined, by Tom Wolfe. Radical empiricism coined 1897 by William James (see empiricism).


1630s, "root part of a word, from radical (adj.) Political sense from 1802; chemical sense from 1816.

Online Etymology Dictionary, © 2010 Douglas Harper

radical in Medicine




A group of elements or atoms usually passing intact from one compound to another but generally incapable of prolonged existence in a free state.
A free radical.


Of or being medical treatment by extreme, drastic, or innovative measures.
Designed to act on or eliminate the root or cause of a pathological process.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

radical in Science



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.

radical in Culture


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


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


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.