radical

Etymology

Inherited from Middle English radical, from Latin rādīcālis (“of or pertaining to the root, having roots, radical”).

Pronunciation

• IPA^(key): /ˈɹædɪkəl/

• Audio (General Australian):

  (file)

• Homophone: radicle

Adjective

radical (comparative more radical, superlative most radical)

1. Favoring fundamental change, or change at the root cause of a matter.

   His beliefs are radical.

   We must be resolute in our fight against radical leftism!

2. (botany, not comparable) Pertaining to a root (of a plant).
3. Pertaining to the basic or intrinsic nature of something.

   Synonym: fundamental

   Antonyms: ignorable, trivial

   • 1790 November, Edmund Burke, Reflections on the Revolution in France, and on the Proceedings in Certain Societies in London Relative to that Event. […], London: […] J[ames] Dodsley, […], →OCLC:

     The most determined exertions of that authority, against them, only showed their radical independence.

4. Thoroughgoing; far-reaching.

   The spread of the cancer required radical surgery, and the entire organ was removed.

   • 2012 January, Donald Worster, “A Drier and Hotter Future”, in American Scientist‎, volume 100, number 1, archived from the original on 26 January 2012, page 70:

     Phoenix and Lubbock are both caught in severe drought, and it is going to get much worse. We may see many such [dust] storms in the decades ahead, along with species extinctions, radical disturbance of ecosystems, and intensified social conflict over land and water. Welcome to the Anthropocene, the epoch when humans have become a major geological and climatic force.

5. (lexicography, not comparable) Of or pertaining to the root of a word.
6. (phonology, phonetics, not comparable, of a sound) Produced using the root of the tongue.

   Coordinate terms: coronal, dorsal, labial, laryngeal

7. (chemistry, not comparable) Involving free radicals.
8. (mathematics) Relating to a radix or mathematical root.

   a radical quantity; a radical sign

9. (slang, 1980s & 1990s) Excellent; awesome.

   That was a radical jump!

Noun

radical (plural radicals)

1. (historical, 19th-century Britain, politics) A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).
2. (historical, early 20th-century France) A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.
3. A person with radical opinions.
4. (arithmetic) A root (of a number or quantity).
6. (linguistics) In logographic writing systems such as the Chinese writing system, the portion of a character (if any) that provides an indication of its meaning, as opposed to phonetic.
   • 2022, R. F. Kuang, Babel, HarperVoyager, page 9:

     The boy recognised the Chinese characters, though the calligraphy looked a bit strange, as if drawn by someone who had seen them and copied them out radical by radical without knowing what they meant.

7. (linguistics) In Celtic languages, the basic, underlying form of an initial consonant which can be further mutated under the Celtic initial consonant mutations.
8. (linguistics) In Semitic languages, any one of the set of consonants (typically three) that make up a root.
9. (chemistry) A group of atoms, joined by covalent bonds, that take part in reactions as a single unit.
10. (organic chemistry) A free radical.
11. (algebra, commutative algebra, ring theory, of an ideal) Given an ideal I in a commutative ring R, another ideal, denoted Rad(I) or ${\displaystyle {\sqrt {I}}}$, such that an element x ∈ R is in Rad(I) if, for some positive integer n, xⁿ ∈ I; equivalently, the intersection of all prime ideals containing I.
12. (algebra, ring theory, of a ring) Given a ring R, an ideal containing elements of R that share a property considered, in some sense, "not good".
13. (algebra, ring theory, of a module) The intersection of maximal submodules of a given module.
14. (number theory) The product of the distinct prime factors of a given positive integer.

References

• “radical”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.
• William Dwight Whitney, Benjamin E[li] Smith, editors (1911), “radical”, in The Century Dictionary […], New York, N.Y.: The Century Co., →OCLC.
• "radical" in Raymond Williams, Keywords (revised), 1983, Fontana Press, page 251.

Further reading

• Radical on Wikipedia.Wikipedia
• Radical of an ideal on Wikipedia.Wikipedia
• Radical of a ring on Wikipedia.Wikipedia
• Radical of a module on Wikipedia.Wikipedia
• Radical of an integer on Wikipedia.Wikipedia
• Radical of an ideal on Encyclopedia of Mathematics
• Ideal Radical on Wolfram MathWorld

Anagrams

• aldaric, cardial

Pronunciation

• IPA^(key): (Central, Balearic) [rə.ðiˈkal]
• IPA^(key): (Valencia) [ra.ðiˈkal]
• Rhymes: -al
• Hyphenation: ra‧di‧cal

Adjective

radical m or f (masculine and feminine plural radicals)

1. radical

Noun

radical m or f by sense (plural radicals)

1. radical

Further reading

• “radical” in Diccionari de la llengua catalana, segona edició, Institut d’Estudis Catalans.
• “radical”, in Gran Diccionari de la Llengua Catalana, Grup Enciclopèdia Catalana, 2025
• “radical” in Diccionari normatiu valencià, Acadèmia Valenciana de la Llengua.
• “radical” in Diccionari català-valencià-balear, Antoni Maria Alcover and Francesc de Borja Moll, 1962.

Etymology

Learned borrowing from Late Latin rādīcālis.

Pronunciation

• IPA^(key): /ʁa.di.kal/
• Rhymes: -al
• Homophones: radicale, radicales

• Audio (Paris):

  (file)

Adjective

radical (feminine radicale, masculine plural radicaux, feminine plural radicales)

1. radical

   L’idéologie islamiste radicale de Boko Haram a provoqué le déplacement de plus de deux millions de personnes dans le nord du Nigeria.

   The radical Islamist ideology of Boko Haram caused more than two million persons to be displaced in northern Nigeria.

Noun

radical m (plural radicaux)

1. (linguistics, grammar) radical, root

Further reading

• “radical”, in Trésor de la langue française informatisé [Digitized Treasury of the French Language], 2012.

Pronunciation

• IPA^(key): /radiˈkal/ [ra.ð̞iˈkɑɫ]
• Rhymes: -al
• Hyphenation: ra‧di‧cal

Noun

radical m (plural radicais)

1. radical (in various senses)

Pronunciation

• Rhymes: (Portugal) -al, (Brazil) -aw
• Hyphenation: ra‧di‧cal

Noun

radical m (plural radicais)

1. (linguistic morphology) stem (main part of a word)
2. (linguistic) radicial (portion of a character)

Noun

radical m or f by sense (plural radicais)

1. radical (person holding unorthodox views)

   Synonym: extremista

Adjective

radical m or f (plural radicais)

1. radical (favouring fundamental change)
2. drastic; extreme
3. (slang) excellent; awesome; thrilling
4. (sports) extreme (dangerous)

Further reading

• “radical”, in Dicionário Priberam da Língua Portuguesa (in Portuguese), Lisbon: Priberam, 2008–2025

Alternative forms

• радикал (radical) — post-1930s Cyrillic spelling

Etymology

Borrowed from French radical or German Radikal.

Pronunciation

• IPA^(key): /ra.diˈkal/
• Rhymes: -al
• Hyphenation: ra‧di‧cal

Adjective

radical m or n (feminine singular radicală, masculine plural radicali, feminine and neuter plural radicale)

1. radical

Etymology

Borrowed from Latin rādīcālis.

Pronunciation

• IPA^(key): /radiˈkal/ [ra.ð̞iˈkal]
• Rhymes: -al
• Syllabification: ra‧di‧cal

Adjective

radical m or f (masculine and feminine plural radicales)

1. radical, seismic

Noun

radical m (plural radicales)

1. radical

Further reading

• “radical”, in Diccionario de la lengua española [Dictionary of the Spanish Language] (in Spanish), online version 23.8, Royal Spanish Academy [Spanish: Real Academia Española], 2024 December 10