(noun, adjective)


1. (used of opinions and actions) far beyond the norm

- radical opinions on education

Similar word(s): immoderate, extremist, ultra

2. markedly new or introducing radical change

- radical political views

Similar word(s): new, revolutionary

3. arising from or going to the root or source

- a radical flaw in the plan

Similar word(s): basic

4. of or relating to or constituting a linguistic root

- a radical verb form

5. 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

- radical leaves

Similar word(s): basal

Sentences with radical as an adjective:

- His beliefs are radical.

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

- a radical quantity; a radical sign

- That was a radical jump!


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

Similar word(s): group

Definition categories: substance, unit

2. 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

Definition categories: substance, atom

3. a person who has radical ideas or opinions

Definition categories: person, individual, mortal, somebody, someone, soul

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

Definition categories: quantity, amount, measure

5. a character conveying the lexical meaning of a logogram

Definition categories: communication, character, graph, grapheme

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

Similar word(s): base, root, stem, theme

Definition categories: communication, descriptor, form, signifier