Emily Dickinson Lexicon

RAD'IC-AL, a. [Fr. from L. radicalis, from radix, root. See Race and Ray.]

1. Pertaining to the root or origin; original; fundamental; as, a radical truth or error; a radical evil; a radical difference of opinions or systems.
2. Implanted by nature; native; constitutional; as, the radical moisture of a body. – Bacon.
3. Primitive; original; underived; uncompounded; as, a radical word.
4. Serving to origination.
5. In botany, proceeding immediately from the root; as, a radical leaf or peduncle. – Martyn.