radical
radical (rădʹĭ-kəl) adjective
1. Arising from or going to a root or source; basic: a radical flaw in a plan; chose the radical solution of starting all over again.
2. Departing markedly from the usual or customary; extreme: radical opinions on education.
3. Favoring or effecting fundamental or revolutionary changes in current practices, conditions, or institutions: radical political views.
4. Linguistics. Of or being a root: a radical form.
5. Botany. Arising from the root or its crown: radical leaves.
noun
1. One who advocates fundamental or revolutionary changes in current practices, conditions, or institutions: radicals seeking to overthrow the social order.
2. Abbr. rad. Mathematics. The root of a quantity as indicated by the radical sign.
3. Symbol R An atom or a group of atoms with at least one unpaired electron.
4. Abbr. rad. Linguistics. See root1.
[Middle English, of a root, from Late Latin rādīcālis, having roots, from Latin rādīx, rādīc-, root.]
radʹically adverb
radʹicalness noun