Arising from or going to a root or source; basic: proposed a radical solution to the problem.
Departing markedly from the usual or customary; extreme: radical opinions on education.
Favoring or effecting fundamental or revolutionary changes in current practices, conditions, or institutions: radical political views.
Linguistics Of or being a root: a radical form.
Botany Arising from the root or its crown: radical leaves.
Slang Excellent; wonderful.
n.
One who advocates fundamental or revolutionary changes in current practices, conditions, or institutions: radicals seeking to overthrow the social order.
Mathematics The root of a quantity as indicated by the radical sign.
Symbol R An atom or a group of atoms with at least one unpaired electron.
[Middle English, of a root, from Late Latin rādīcālis, having roots, from Latin rādīx, rādīc-, root; see wrād- in Indo-European roots.] rad'i·cal·ly adv., rad'i·cal·ness n.
[rad-ik-lee] 
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