rad·i·cal

[rad-i-kuhl]
adjective
1.
of or going to the root or origin; fundamental: a radical difference.
2.
thoroughgoing or extreme, especially as regards change from accepted or traditional forms: a radical change in the policy of a company.
3.
favoring drastic political, economic, or social reforms: radical ideas; radical and anarchistic ideologues.
4.
forming a basis or foundation.
5.
existing inherently in a thing or person: radical defects of character.
6.
Mathematics.
a.
pertaining to or forming a root.
b.
denoting or pertaining to the radical sign.
c.
irrational ( def 5b ).
7.
Grammar. of or pertaining to a root.
8.
Botany. of or arising from the root or the base of the stem.
noun
9.
a person who holds or follows strong convictions or extreme principles; extremist.
10.
a person who advocates fundamental political, economic, and social reforms by direct and often uncompromising methods.
11.
Mathematics.
a.
a quantity expressed as a root of another quantity.
b.
the set of elements of a ring, some power of which is contained in a given ideal.
c.
radical sign.
12.
Chemistry.
a.
group ( def 3 ).
b.
free radical.
13.
Grammar, root ( def 11 ).
14.
(in Chinese writing) one of 214 ideographic elements used in combination with phonetics to form thousands of different characters.
00:10
Radical is always a great word to know.
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common people
going rapidly over something, without noticing details; hasty; superficial:
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Origin:
1350–1400; Middle English < Late Latin rādīcālis having roots, equivalent to Latin rādīc- (stem of rādīx) root1 + -ālis -al1

Related forms
rad·i·cal·ness, noun
half-rad·i·cal, adjective
half-rad·i·cal·ly, adverb
mul·ti·rad·i·cal, adjective
non·rad·i·cal, adjective, noun
non·rad·i·cal·ness, noun
qua·si-rad·i·cal, adjective
qua·si-rad·i·cal·ly, adverb
sem·i·rad·i·cal, adjective
sem·i·rad·i·cal·ly, adverb
sem·i·rad·i·cal·ness, noun
sub·rad·i·cal, adjective
sub·rad·i·cal·ness, noun
su·per·rad·i·cal, adjective
su·per·rad·i·cal·ly, adverb
su·per·rad·i·cal·ness, noun
ul·tra·rad·i·cal, adjective, noun
ul·tra·rad·i·cal·ly, adverb
un·rad·i·cal, adjective
un·rad·i·cal·ly, adverb

Synonyms
1. basic, essential; original, innate, ingrained. 2. complete, unqualified, thorough; drastic, excessive, immoderate, violent. 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
1, 2. superficial.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2013.
Cite This Source Link To Radical
Collins
World English Dictionary
radical (ˈrædɪkəl) [Click for IPA pronunciation guide]
 
—adj
1.  of, relating to, or characteristic of the basic or inherent constitution of a person or thing; fundamental: a radical fault
2.  concerned with or tending to concentrate on fundamental aspects of a matter; searching or thoroughgoing: radical thought; a radical re-examination
3.  favouring or tending to produce extreme or fundamental changes in political, economic, or social conditions, institutions, habits of mind, etc: a radical party
4.  med (of treatment) aimed at removing the source of a disease: radical surgery
5.  slang chiefly (US) very good; excellent
6.  of, relating to, or arising from the root or the base of the stem of a plant: radical leaves
7.  maths of, relating to, or containing roots of numbers or quantities
8.  linguistics of or relating to the root of a word
 
—n
9.  a person who favours extreme or fundamental change in existing institutions or in political, social, or economic conditions
10.  maths a root of a number or quantity, such as ³√5, √x
11.  chem Also: radicle
 a.  short for free radical
 b.  another name for group
12.  linguistics another word for root
13.  (in logographic writing systems such as that used for Chinese) a part of a character conveying lexical meaning
 
[C14: from Late Latin rādīcālis having roots, from Latin rādix a root]
 
'radicalness
 
—n

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Etymonline
Word Origin & History

radical
late 14c. (adj.), in a medieval philosophical sense, from L.L. radicalis "of or having roots," from L. radix (gen. radicis) "root" (see radish). Meaning "going to the origin, essential" is from 1650s. Political sense of "reformist" (via notion of "change from the roots")
is first recorded 1802 (n.), 1820 (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.
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

radical rad·i·cal (rād'ĭ-kəl)
n.
Abbr. R

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

  2. A free radical.

adj.

  1. Of or being medical treatment by extreme, drastic, or innovative measures.

  2. 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.
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American Heritage
Science Dictionary
radical   (rād'ĭ-kəl)  Pronunciation Key 

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

  2. 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 © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary

radical definition


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

radical definition


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

Note: In general, radicals are associated with chemical reactions that proceed rapidly.
The American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
Cite This Source
Slang Dictionary

radical definition


  1. mod.
    great; excellent. (California.) : My boyfriend, he's, like, so radical!
Dictionary of American Slang and Colloquial Expressions by Richard A. Spears.Fourth Edition.
Copyright 2007. Published by McGraw Hill.
Cite This Source
Example sentences
It might be uncomfortable and take a bit of work, but our future depends on
  this radical change in order to survive.
Moreover, such a change would in fact be less radical than it might at first
  appear.
Both they and their voters avoid radical change whenever possible.
When it comes to radical energy solutions, an extreme long shot is a nuclear
  power scheme that would combine fusion and fission.
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