radically

UK: /ˈrædɪkəli/ US: (rad′ik lē)

WordReference Random House Unabridged Dictionary of American English © 2025

rad•i•cal•ly  (rad′ik lē), adj. 

1. with regard to origin or root.
2. in a complete or basic manner;
   thoroughly;
   fundamentally.

• radical + -ly 1600–10

Collins Concise English Dictionary © HarperCollins Publishers::

radically / ˈrædɪkəlɪ/ adverb

1. thoroughly; completely; fundamentally: to alter radically

WordReference Random House Learner's Dictionary of American English © 2025

rad•i•cal /ˈrædɪkəl/   adj. 

1. thoroughgoing, complete, or extreme:
   a radical change in policy.
2. Government favoring drastic or extreme political, economic, or social reforms:
   radical politics.
3. basic;
   fundamental:
   [usually: before a noun] radical defects of character.
4. Slang Terms great;
   marvelous;
   wonderful:
   a radical dude.

n. [countable]

5. a person who holds or follows extreme convictions, beliefs, or principles;
   extremist.
6. Mathematics
   • a quantity expressed as a root of another quantity.
   • radical sign.
7. Chemistry a group of atoms that act together as a unit.
8. Linguistics (in Chinese writing) one of 214 elements that have meaning or sense, and are used with elements representing sounds to form thousands of different characters.

rad•i•cal•ism, n. [uncountable]
rad•i•cal•ly, adv. 

WordReference Random House Unabridged Dictionary of American English © 2025

rad•i•cal  (rad′i kəl), adj. 

1. of or going to the root or origin;
   fundamental:
   a radical difference.
2. thoroughgoing or extreme, esp. as regards change from accepted or traditional forms:
   a radical change in the policy of a company.
3. Government 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
   • pertaining to or forming a root.
   • denoting or pertaining to the radical sign.
   • 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.

n. 

9. a person who holds or follows strong convictions or extreme principles;
   extremist.
10. Government a person who advocates fundamental political, economic, and social reforms by direct and often uncompromising methods.
11. 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.
    • See radical sign. 
12. Chemistry
    • group (def. 3).
    • See free radical. 
13. Grammar root (def. 11).
14. Linguistics (in Chinese writing) one of 214 ideographic elements used in combination with phonetics to form thousands of different characters.

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

rad′i•cal•ness, n. 
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, esp. 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.