RADICAL

Definitions

1. 1. A primitive word; a radix, root, or simple, underived, uncompounded word; an etymon.
2. 2. A primitive letter; a letter that belongs to the radix. The words we at present make use of, and understand only by common agreement, assume a new air and life in the understanding, when you trace them to their radicals, where you find every word strongly stamped with nature; full of energy, meaning, character, painting, and poetry. Cleland.
3. 3. One who advocates radical changes in government or social institutions, especially such changes as are intended to level class inequalities; -- opposed to conservative. In politics they [the Independents] were, to use phrase of their own time. "Root-and-Branch men," or, to use the kindred phrase of our own, Radicals. Macaulay.
4. 4. A characteristic, essential, and fundamental constituent of any compound; hence, sometimes, an atom. As a general rule, the metallic atoms are basic radicals, while the nonmetallic atoms are acid radicals. J. P. Cooke.
5. 5. Specifically, a group of two or more atoms, not completely saturated, which are so linked that their union implies certain properties, and are conveniently regarded as playing the part of a single atom; a residue; -- called also a compound radical. Cf. Residue.
6. 6. A radical quantity. See under Radical, a. An indicated root of a perfect power of the degree indicated is not a radical but a rational quantity under a radical form. Davies & Peck (Math. Dict. )
7. 7. A radical vessel. See under Radical, a.