radical Meaning, Definition & Usage

  1. noun (chemistry) two or more atoms bound together as a single unit and forming part of a molecule
    chemical group; group.
  2. noun an atom or group of atoms with at least one unpaired electron; in the body it is usually an oxygen molecule that has lost an electron and will stabilize itself by stealing an electron from a nearby molecule
    free radical.
    • in the body free radicals are high-energy particles that ricochet wildly and damage cells
  3. noun a person who has radical ideas or opinions
  4. noun (mathematics) a quantity expressed as the root of another quantity
  5. noun a character conveying the lexical meaning of a logogram
  6. noun (linguistics) the form of a word after all affixes are removed
    root word; stem; theme; base; root.
    • thematic vowels are part of the stem
  7. adjective satellite (used of opinions and actions) far beyond the norm
    extremist; ultra.
    • extremist political views
    • radical opinions on education
    • an ultra conservative
  8. adjective satellite markedly new or introducing radical change
    revolutionary.
    • a revolutionary discovery
    • radical political views
  9. adjective satellite arising from or going to the root or source
    • a radical flaw in the plan
  10. adjective of or relating to or constituting a linguistic root
    • a radical verb form
  11. adjective especially of leaves; located at the base of a plant or stem; especially arising directly from the root or rootstock or a root-like stem
    basal.
    • basal placentation
    • radical leaves

WordNet

Rad"i*cal adjective
Etymology
F., fr. L. radicalis having roots, fr. radix, -icis, a root. See Radix.
Definitions
  1. Of or pertaining to the root; proceeding directly from the root.
  2. 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.
    The most determined exertions of that authority, against them, only showed their radical independence. Burke.
  3. (Bot.) (a) Belonging to, or proceeding from, the root of a plant; as, radical tubers or hairs. (b) 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.
  4. (Philol.) Relating, or belonging, to the root, or ultimate source of derivation; as, a radical verbal form.
  5. (Math.) Of or pertaining to a radix or root; as, a radical quantity; a radical sign. See below. Syn. -- Primitive; original; natural; underived; fundamental; entire. -- Radical, Entire. These words are frequently employed as interchangeable in describing some marked alternation in the condition of things. There is, however, an obvious difference between them. A radical cure, reform, etc., is one which goes to the root of the thing in question; and it is entire, in the sense that, by affecting the root, it affects in a appropriate degree the entire body nourished by the root; but it may not be entire in the sense of making a change complete in its nature, as well as in its extent. Hence, we speak of a radical change; a radical improvement; radical differences of opinion; while an entire change, an entire improvement, an entire difference of opinion, might indicate more than was actually intended. A certain change may be both radical and entire, in every sense.
Rad"i*cal noun
Definitions
  1. (Philol.) (a) A primitive word; a radix, root, or simple, underived, uncompounded word; an etymon. (b) 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.
  2. (Politics) 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.
  3. (Chem.) (a) 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.
    (b) 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.
  4. (Alg.) 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. )
  5. (Anat.) A radical vessel. See under Radical, a.

Webster 1913