definition of
radical

[1] #1 radical n. [group, chemical group] (chemistry) two or more atoms bound together as a single unit and forming part of a molecule. wn

[2] #2 radical n. [free radical] 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 part. wn

[3] #3 radical n. a person who has radical ideas or opinions. wn

[4] #4 radical n. (mathematics) a quantity expressed as the root of another quantity. wn

[5] #5 radical a. of or relating to or constituting a linguistic root; "a radical verb form". wn