adj a radical vessel. ·see under radical, ·adj.
2. radical ·noun a radical quantity. ·see under radical, ·adj.
3. radical ·noun a primitive letter; a letter that belongs to the radix.
4. radical ·adj of or pertaining to the root; proceeding directly from the root.
5. radical ·adj belonging to, or proceeding from, the root of a plant; as, radical tubers or hairs.
6. radical ·adj relating, or belonging, to the root, or ultimate source of derivation; as, a radical verbal form.
7. radical ·noun a primitive word; a radix, root, or simple, underived, uncompounded word; an etymon.
8. radical ·adj of or pertaining to a radix or root; as, a radical quantity; a radical sign. ·see below.
9. radical ·noun a characteristic, essential, and fundamental constituent of any compound; hence, sometimes, an atom.
10. radical ·adj proceeding from a rootlike stem, or one which does not rise above the ground; as, the radical leaves of the dandelion and the sidesaddle flower.
11. radical ·noun one who advocates radical changes in government or social institutions, especially such changes as are intended to level class inequalities;
opposed to conservative.
12. radical ·adj hence: of or pertaining to the root or origin; reaching to the center, to the foundation, to the ultimate sources, to the principles, or the like; original; fundamental; thorough-going; unsparing; extreme; as, radical evils; radical reform; a radical party.
13. radical ·noun 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.