Definition of radicals:
(adj) :
Favoring fundamental change, or change at the root cause of a matter.
(adj) :
(botany, not comparable) Pertaining to a root (of a plant).
(adj) :
Pertaining to the basic or intrinsic nature of something.
(adj) :
Thoroughgoing; far-reaching.
(adj) :
(lexicography, not comparable) Of or pertaining to the root of a word.
(adj) :
(phonology, phonetics, not comparable, of a sound) Produced using the root of the tongue.