Noun
1. (chemistry) two or more atoms bound together as a single unit and forming part of a molecule
2. 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"3. a person who has radical ideas or opinions
4. a character conveying the lexical meaning of a logogram
5. a sign placed in front of an expression to denote that a root is to be extracted
6. (linguistics) the form of a word after all affixes are removed;
"thematic vowels are part of the stem"Adjective
1. (used of opinions and actions) far beyond the norm;
"extremist political views""radical opinions on education""an ultra conservative"2. markedly new or introducing radical change;
"a revolutionary discovery""radical political views"3. arising from or going to the root;
"a radical flaw in the plan"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;
"basal placentation""radical leaves"