Adjective radical has 5 senses
  1. extremist, radical, ultra - (used of opinions and actions) far beyond the norm; "extremist political views"; "radical opinions on education"; "an ultra conservative"
    Antonym: moderate (indirect, via immoderate)
  2. revolutionary, radical - markedly new or introducing radical change; "a revolutionary discovery"; "radical political views"
    Antonym: old (indirect, via new)
  3. radical - arising from or going to the root; "a radical flaw in the plan"
    incidental, incident (indirect, via basic)
  4. radical - of or relating to or constituting a linguistic root; "a radical verb form"
  5. radical, basal - 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"
    Antonym: cauline
,Noun radical has 6 senses
  1. group, radical, chemical group - (chemistry) two or more atoms bound together as a single unit and forming part of a molecule
    --1 is a kind of unit, building block
    --1 is a part of molecule
    --1 has particulars:
     acyl, acyl group; alcohol group, alcohol radical; aldehyde group, aldehyde radical; alkyl, alkyl group, alkyl radical; allyl, allyl group, allyl radical; amino, amino group; azido group, azido radical; azo group, azo radical; benzyl, benzyl group, benzyl radical; benzoyl group, benzoyl radical; cacodyl, cacodyl group, cacodyl radical, arsenic group; carbonyl group; carboxyl, carboxyl group; chromophore; cyano group, cyano radical, cyanide group, cyanide radical; glyceryl; hydrazo group, hydrazo radical; hydroxyl, hydroxyl group, hydroxyl radical; ketone group; methylene group, methylene radical, methylene; propyl, propyl group, propyl radical; butyl; nitro group; nitrite; uranyl, uranyl group, uranyl radical; vinyl, vinyl group, vinyl radical
  2. free radical, radical - an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule than 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"
    --2 is a kind of atom
  3. radical - a person who has radical ideas or opinions
    --3 is a kind of
    person, individual, someone, somebody, mortal, human, soul
    --3 has particulars:
     anarchist, nihilist, syndicalist; Bolshevik, Marxist, pinko, red, bolshie; extremist; leveler, leveller; revolutionist, revolutionary, subversive, subverter; terrorist; Trotskyite, Trotskyist, Trot; Wobbly; Young Turk
  4. radical - a character conveying the lexical meaning of a logogram
    --4 is a kind of
    character, grapheme, graphic symbol
    --4 is a part of ideogram, ideograph
  5. radical, radical sign - a sign placed in front of an expression to denote that a root is to be extracted
    --5 is a kind of mathematical notation
  6. root, root word, base, stem, theme, radical - (linguistics) the form of a word after all affixes are removed; "thematic vowels are part of the stem"
    --6 is a kind of form, word form, signifier, descriptor