[ rad-i-kuhl ]
/ ˈræd ɪ kəl /



Nearby words

  1. radiative zone,
  2. radiator,
  3. radiator grille,
  4. radiatory,
  5. radiatus,
  6. radical axis,
  7. radical chic,
  8. radical empiricism,
  9. radical expression,
  10. radical hysterectomy

Origin of radical

1350–1400; Middle English < Late Latin rādīcālis “having roots,” equivalent to Latin rādīc- (stem of rādīx) root1 + -ālis -al1

Related forms

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.

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

Examples from the Web for radical

British Dictionary definitions for radical


/ (ˈrædɪkəl) /



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
Online Etymology Dictionary, © 2010 Douglas Harper

Medicine definitions for radical


[ rădĭ-kəl ]


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.

Science definitions for radical


[ rădĭ-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.

Culture definitions for radical


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.