Princeton's WordNet

1. group, radical, chemical group(noun)

   (chemistry) two or more atoms bound together as a single unit and forming part of a molecule

2. free radical, radical(noun)

   an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule that has lost an electron and will stabilize itself by stealing an electron from a nearby molecule

   "in the body free radicals are high-energy particles that ricochet wildly and damage cells"

3. radical(noun)

   a person who has radical ideas or opinions

4. radical(noun)

   (mathematics) a quantity expressed as the root of another quantity

5. radical(noun)

   a character conveying the lexical meaning of a logogram

6. root, root word, base, stem, theme, radical(adj)

   (linguistics) the form of a word after all affixes are removed

   "thematic vowels are part of the stem"

7. extremist, radical, ultra(adj)

   (used of opinions and actions) far beyond the norm

   "extremist political views"; "radical opinions on education"; "an ultra conservative"

8. revolutionary, radical(adj)

   markedly new or introducing radical change

   "a revolutionary discovery"; "radical political views"

9. radical(adj)

   arising from or going to the root or source

   "a radical flaw in the plan"

10. radical(adj)

    of or relating to or constituting a linguistic root

    "a radical verb form"

11. radical, basal(adj)

    especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem

    "basal placentation"; "radical leaves"

Kernerman English Learner's Dictionary

1. radical(adjective)ˈræd ɪ kəl

   extreme

   radical political beliefs

2. radicalˈræd ɪ kəl

   major or very great

   radical changes

Wiktionary

1. radical(Noun)

   A member of the most progressive wing of the Liberal Party; someone favouring social reform (but generally stopping short of socialism).

2. radical(Noun)

   A member of an influential, centrist political party favouring moderate social reform, a republican constitution, and secular politics.

3. radical(Noun)

   A person with radical opinions.

4. radical(Noun)

   A root (of a number or quantity).

5. radical(Noun)

   In logographic writing systems as the Chinese writing system, the portion of a character (if any) that provides an indication of its meaning, as opposed to phonetic.

6. radical(Noun)

   In Semitic languages, any one of the set of consonants (typically three) that make up a root.

7. radical(Noun)

   A group of atoms, joined by covalent bonds, that take part in reactions as a single unit.

8. radical(Noun)

   A free radical.

9. radical(Adjective)

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

   His beliefs are radical.

10. radical(Adjective)

    Of or pertaining to a root .

11. radical(Adjective)

    Of or pertaining to the intrinsic nature of something.

12. radical(Adjective)

    Thoroughgoing.

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

13. radical(Adjective)

    Of or pertaining to the root of a word.

14. radical(Adjective)

    Involving free radicals

15. radical(Adjective)

    Excellent.

    That was a radical jump!

Origin: From radical, from radicalis, from radix; see radix.

Webster Dictionary

1. Radical(adj)

   of or pertaining to the root; proceeding directly from the root

2. Radical(adj)

   hence: Of or pertaining to the root or origin; reaching to the center, to the foundation, to the ultimate sources, to the principles, or the like; original; fundamental; thorough-going; unsparing; extreme; as, radical evils; radical reform; a radical party

3. Radical(adj)

   belonging to, or proceeding from, the root of a plant; as, radical tubers or hairs

4. Radical(adj)

   proceeding from a rootlike stem, or one which does not rise above the ground; as, the radical leaves of the dandelion and the sidesaddle flower

5. Radical(adj)

   relating, or belonging, to the root, or ultimate source of derivation; as, a radical verbal form

6. Radical(adj)

   of or pertaining to a radix or root; as, a radical quantity; a radical sign. See below

7. Radical(noun)

   a primitive word; a radix, root, or simple, underived, uncompounded word; an etymon

8. Radical(noun)

   a primitive letter; a letter that belongs to the radix

9. Radical(noun)

   one who advocates radical changes in government or social institutions, especially such changes as are intended to level class inequalities; -- opposed to conservative

10. Radical(noun)

    a characteristic, essential, and fundamental constituent of any compound; hence, sometimes, an atom

11. Radical(noun)

    specifically, a group of two or more atoms, not completely saturated, which are so linked that their union implies certain properties, and are conveniently regarded as playing the part of a single atom; a residue; -- called also a compound radical. Cf. Residue

12. Radical(noun)

    a radical quantity. See under Radical, a

13. Radical(adj)

    a radical vessel. See under Radical, a

• wesenlikAfrikaans
• أساسيArabic
• корененBulgarian
• radicalPortuguese (BR)
• základníCzech
• fundamentalGerman
• grundlæggendeDanish
• ριζικός, βασικόςGreek
• radical, fundamentalSpanish
• põhimõttelineEstonian
• اصلیFarsi
• perinpohjainenFinnish
• fondamentalFrench
• יְסוֹדִיHebrew
• आधारिकHindi
• radikalan, temeljanCroatian
• gyökeresHungarian
• mendasarIndonesian
• grundvallar-Icelandic
• radicaleItalian
• 根本的なJapanese
• 근원적인Korean
• esminisLithuanian
• būtisksLatvian
• radikalMalay
• radiatorDutch
• grunnleggendeNorwegian
• podstawowy, zasadniczyPolish
• اصلیPersian
• اساسى، بنيادى، دراډيكال ګوندغړى، داساسى اوبنيادى سمون غوښتونكىPashto
• radicalPortuguese
• esenţialRomanian
• кореннойRussian
• základnýSlovak
• bistvenSlovenian
• radikalanSerbian
• grundläggande, fundamentalSwedish
• โดยรากฐานThai
• temel, asılTurkish
• 根本的Chinese (Trad.)
• корінний; основнийUkrainian
• بنیادیUrdu
• cơ bảnVietnamese
• 基本的Chinese (Simp.)