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American Heritage Dictionary - Cite This Source - Share This

rad·i·cal       (rād'ĭ-kəl)  Pronunciation Key  adj.   Arising from or going to a root or source; basic: proposed a radical solution to the problem. Departing markedly from the usual or customary; extreme: radical opinions on education. Favoring or effecting fundamental or revolutionary changes in current practices, conditions, or institutions: radical political views. Linguistics Of or being a root: a radical form. Botany Arising from the root or its crown: radical leaves. Slang Excellent; wonderful. n.   One who advocates fundamental or revolutionary changes in current practices, conditions, or institutions: radicals seeking to overthrow the social order. Mathematics The root of a quantity as indicated by the radical sign. Symbol R An atom or a group of atoms with at least one unpaired electron. Linguistics See root1. [Middle English, of a root, from Late Latin rādīcālis, having roots, from Latin rādīx, rādīc-, root; see wrād- in Indo-European roots.] rad'i·cal·ly adv., rad'i·cal·ness n.

American Heritage Dictionary - Cite This Source - Share This

root 1       (rōōt, rŏŏt)  Pronunciation Key  n.   The usually underground portion of a plant that lacks buds, leaves, or nodes and serves as support, draws minerals and water from the surrounding soil, and sometimes stores food. Any of various other underground plant parts, especially an underground stem such as a rhizome, corm, or tuber. The embedded part of an organ or structure such as a hair, tooth, or nerve, that serves as a base or support. A base or support: We snipped the wires at the roots. The condition of being settled and of belonging to a particular place or society. Often used in the plural: Our roots in this town go back a long way. roots The state of having or establishing an indigenous relationship with or a personal affinity for a particular culture, society, or environment: music with unmistakable African roots. The element that carries the main component of meaning in a word and provides the basis from which a word is derived by adding affixes or inflectional endings or by phonetic change. Such an element reconstructed for a protolanguage. Also called radical. A number that when multiplied by itself an indicated number of times forms a product equal to a specified number. For example, a fourth root of 4 is √2. Also called nth root. A number that reduces a polynomial equation in one variable to an identity when it is substituted for the variable. A number at which a polynomial has the value zero. The note from which a chord is built. Such a note occurring as the lowest note of a triad or other chord. An essential part or element; the basic core: I finally got to the root of the problem. A primary source; an origin. See Synonyms at origin. A progenitor or ancestor from which a person or family is descended. The condition of being settled and of belonging to a particular place or society. Often used in the plural: Our roots in this town go back a long way. roots The state of having or establishing an indigenous relationship with or a personal affinity for a particular culture, society, or environment: music with unmistakable African roots. The element that carries the main component of meaning in a word and provides the basis from which a word is derived by adding affixes or inflectional endings or by phonetic change. Such an element reconstructed for a protolanguage. Also called radical. A number that when multiplied by itself an indicated number of times forms a product equal to a specified number. For example, a fourth root of 4 is √2. Also called nth root. A number that reduces a polynomial equation in one variable to an identity when it is substituted for the variable. A number at which a polynomial has the value zero. The note from which a chord is built. Such a note occurring as the lowest note of a triad or other chord. Linguistics The element that carries the main component of meaning in a word and provides the basis from which a word is derived by adding affixes or inflectional endings or by phonetic change. Such an element reconstructed for a protolanguage. Also called radical. A number that when multiplied by itself an indicated number of times forms a product equal to a specified number. For example, a fourth root of 4 is √2. Also called nth root. A number that reduces a polynomial equation in one variable to an identity when it is substituted for the variable. A number at which a polynomial has the value zero. The note from which a chord is built. Such a note occurring as the lowest note of a triad or other chord. Mathematics A number that when multiplied by itself an indicated number of times forms a product equal to a specified number. For example, a fourth root of 4 is √2. Also called nth root. A number that reduces a polynomial equation in one variable to an identity when it is substituted for the variable. A number at which a polynomial has the value zero. The note from which a chord is built. Such a note occurring as the lowest note of a triad or other chord. Music The note from which a chord is built. Such a note occurring as the lowest note of a triad or other chord. v.   root·ed, root·ing, roots v.   intr. To grow roots or a root. To become firmly established, settled, or entrenched. To come into existence; originate. v.   tr. To cause to put out roots and grow. To implant by or as if by the roots. To furnish a primary source or origin to. To remove by or as if by the roots. Often used with up or out: "declared that waste and fraud will be vigorously rooted out of Government" (New York Times). [Middle English rot, from Old English rōt, from Old Norse; see wrād- in Indo-European roots.] root'er n.

Online Etymology Dictionary - Cite This Source - Share This
radical 

WordNet - Cite This Source - Share This

radical
adjective
1.	(used of opinions and actions) far beyond the norm; "extremist political views"; "radical opinions on education"; "an ultra conservative" [syn: extremist]
2.	markedly new or introducing radical change; "a revolutionary discovery"; "radical political views" [syn: revolutionary]
3.	arising from or going to the root or source; "a radical flaw in the plan"
4.	of or relating to or constituting a linguistic root; "a radical verb form"
5.	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 placentation"; "radical leaves" [ant: cauline]
noun
1.	(chemistry) two or more atoms bound together as a single unit and forming part of a molecule [syn: group]
2.	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; "in the body free radicals are high-energy particles that ricochet wildly and damage cells" [syn: free radical]
3.	a person who has radical ideas or opinions
4.	(mathematics) a quantity expressed as the root of another quantity
5.	a character conveying the lexical meaning of a logogram
6.	(linguistics) the form of a word after all affixes are removed; "thematic vowels are part of the stem" [syn: root]

The American Heritage Science Dictionary - Cite This Source - Share This

radical       (rād'ĭ-kəl)  Pronunciation Key  A root, such as √2, especially as indicated by a radical sign (√). A group of atoms that behaves as a unit in chemical reactions and is often not stable except as part of a molecule. The hydroxyl, ethyl, and phenyl radicals are examples. Radicals are unchanged by chemical reactions.

American Heritage New Dictionary of Cultural Literacy, Third Edition - Cite This Source - Share This
radical

In politics, someone who demands substantial or extreme changes in the existing system.

American Heritage New Dictionary of Cultural Literacy, Third Edition - Cite This Source - Share This
radical

In chemistry, an atom or group of atoms that has at least one electron free to participate in forming a chemical bond.

Note: In general, radicals are associated with chemical reactions that proceed rapidly.

American Heritage Stedman's Medical Dictionary - Cite This Source - Share This

radical rad·i·cal (rād'ĭ-kəl)
n.
Abbr. R

1. A group of elements or atoms usually passing intact from one compound to another but generally incapable of prolonged existence in a free state.
2. A free radical.

adj.

1. Of or being medical treatment by extreme, drastic, or innovative measures.
2. Designed to act on or eliminate the root or cause of a pathological process.

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Radical

Rad"i*cal\, a. [F., fr. L. radicalis having roots, fr. radix, -icis, a root. See Radix.]

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.

Radical axis of two circles. (Geom.) See under Axis.

Radical pitch, the pitch or tone with which the utterance of a syllable begins. --Rush.

Radical quantity (Alg.), a quantity to which the radical sign is prefixed; specifically, a quantity which is not a perfect power of the degree indicated by the radical sign; a surd.

Radical sign (Math.), the sign [root] (originally the letter r, the initial of radix, root), placed before any quantity, denoting that its root is to be extracted; thus, [root]a, or [root](a + b). To indicate any other than the square root, a corresponding figure is placed over the sign; thus [cuberoot]a, indicates the third or cube root of a.

Radical stress (Elocution), force of utterance falling on the initial part of a syllable or sound.

Radical vessels (Anat.), minute vessels which originate in the substance of the tissues.

Syn: Primitive; original; natural; underived; fundamental; entire.

Usage: 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.

Webster's Revised Unabridged Dictionary - Cite This Source - Share This

Radical

Rad"i*cal\, n. 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.